Table of Content

20 September 2022, Volume 31 Issue 9

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A taxonomic inventory of national key protected wild plants in Qinghai Province， based on the national checklist of key protected wild plants （2021）

Jin-yuan CHEN, Wei-bo DU, Xu SU

2022, 31(9):  1-12.  DOI: 10.11686/cyxb2021502

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Following the new national checklist of key protected wild plants， we made a taxonomic inventory of key nationally protected wild plants in the Qinghai Province. Data was drawn from consulting relevant literature and inspection of herbarium specimens. Our aim was to better understand their plant types， family and genus distribution， endemism， conservation status， and geographical distribution. It was found that： 1） Compared with species checklists in 1999， 44 key nationally protected wild species are newly added into the species list for Qinghai Province. 2） In Qinghai Province there are 53 species and one variety， 30 genera， 22 families and three categories of key nationally protected wild plants listed. Among them， Nostoc flagelliforme is a level-one key protected wild plant， and 52 species and one variety are level-two key protected wild plants. 3） The family with the largest number of plants listed is the Orchidaceae with 10 species， and the most commonly listed genus is Cypripedium containing eight species. 4） There is one genus endemic to China， there are three genera endemic to China and the Qinghai-Tibet Plateau （QTP）， nine species endemic to China， nine species endemic to the QTP， 13 species endemic to China and the QTP and one species， Meconopsis barbiseta， endemic to Qinghai Province. 5） With respect to conservation status， there are 18 species listed as vulnerable （VU） level， and 12 species listed as endangered （EN） among the 54 key nationally protected wild species from Qinghai Province， which accounted for 55.55% of the total species. 6） Most of the key nationally protected wild species are distributed mainly in the alpine grassland and forest vegetation of Yushu and Golog Tibetan Autonomous Prefecture and Haidong city， which is consistent with the plant diversity distribution pattern in Qinghai Province. There are 53 species and one variety of key nationally protected wild plants in Qinghai Province， most of which are level-two key protected wild plants. Among these， 32 species are endemic species， accounting for 59.25% of the total， and 30 species are among the threatened species. Most of the key nationally protected wild plants are distributed in the southeast of Qinghai Province.

Effects of Alternanthera philoxeroides invasion on plant diversity in the riparian zones of downtown Chongqing in the Three Gorges Reservoir area

Li-miao ZHANG, Xue TAN, Zhi DONG, Jie ZHENG, Zhong-xun YUAN, Chang-xiao LI

2022, 31(9):  13-25.  DOI: 10.11686/cyxb2021447

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To assess the impact of the Alternanthera philoxeroides invasion on the species composition and diversity in the urban riparian zone， 47 sample sites in the riparian zones of downtown Chongqing in the Three Gorges Reservoir area of China were investigated. The results were as follows： 1） In the main waterway riparian zones， both the Patrick richness index and the Shannon-Wiener diversity index were significantly lower than in the tributary riparian zones， and the Pielou evenness index in the main waterway riparian zone was significantly higher than in the tributary riparian zone. There was no significant difference in the Simpson diversity index between the main waterway and the tributary riparian zone. 2） As the cover of invading A. philoxeroides increased， the Simpson diversity index， Shannon-Wiener diversity index， and Pielou evenness index of the main waterway and tributary riparian zones fell， after initially rising， and each diversity index’s invasion threshold differed. While the Patrick richness index dropped significantly in the tributary， the main waterway had no significant change. 3） The main soil factors affecting the species diversity of the main waterway riparian zone were organic matter， nitrate nitrogen， and total nitrogen. The main soil factors affecting the species diversity of the tributary riparian zone were soil moisture， total nitrogen and available phosphorus. 4） The invasion of A. philoxeroides was mainly correlated with available potassium， organic matter， and total nitrogen in the main waterway riparian zone. In contrast， it was more correlated with available phosphorus， available potassium， and total nitrogen in the tributary riparian zone. Our studies have shown that A. philoxeroides is more likely to invade habitats with high soil nutrient content. A mild invasion of A. philoxeroides promotes species diversity in urban riparian zones. In contrast， moderate and severe invasions will reduce species diversity， especially in tributary riparian zones. Thus， we should do more work to keep track of this invasive species and develop effective and practical ways to stop it from spreading.

Effect of nitrogen application rate on dry matter accumulation， allocation and water use efficiency of forage sorghum

Wei GAO, Na SHOU, Cong-ze JIANG, Ren-shi MA, Yu-ying SHEN, Xian-long YANG

2022, 31(9):  26-35.  DOI: 10.11686/cyxb2021374

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To ascertain the appropriate N fertilizer rate for forage sorghum （Sorghum bicolor） production in dry regions of the Longdong Loess Plateau， a two-year field experiment was conducted at the Qingyang National Field Station of Grassland Agroecosystem during 2019 and 2020 to determine the effects of different N fertilizer application rates on dry matter accumulation， allocation， water consumption， and water use efficiency of forage sorghum cultivar ‘F10’. Five N application rates： 0， 80， 160， 240， and 320 kg·ha^-1 （denoted N₀， N₈₀， N₁₆₀， N₂₄₀， and N₃₂₀， respectively）， were used in this study， and each treatment was replicated three times using a randomized complete block design. In both seasons， dry matter accumulation （DMA） of forage sorghum at the jointing， heading， flowering， and filling stages showed an increasing trend with successive increments in N application rate. At the harvest stage in 2019 and 2020， the DMA of forage sorghum increased initially and then decreased with further increase in N application rate， and DMA peaked at N₁₆₀ with values of 22.3 t·ha^-1 in 2019 and 18.0 t·ha^-1 in 2020. As the growing season progressed， dry matter proportion （DMP） of leaves in forage sorghum gradually decreased， while DMP of stems initially increased and then decreased. At the harvest stages， the DMP of stems was the highest with average values of 70.8% in 2019 and 73.8% in 2020. In 2019， compared to N₀， the N fertilization treatments significantly increased DMP of ears and decreased DMP of stems， however， no significant difference was observed in 2020. In 2019， there were no significant differences in water consumption （WC） and water consumption rate （WCR） of forage sorghum among the different treatments. In 2020， the WC of forage sorghum in the treatments varied from 483.4 to 505.8 mm， and the WCR varied from 3.1 to 3.3 mm·d^-1. Compared to N₀， the WC in 2020 was significantly increased by 4.6% in N₈₀ and by 3.9% in N₃₂₀， respectively， and the WCR in 2020 was significantly increased by 6.5% in both N₈₀ and N₃₂₀. The water use efficiency （WUE） of forage sorghum at N₁₆₀ was the highest with values of 42.9 kg·ha^-1·mm^-1 in 2019 and 36.4 kg·ha^-1·mm^-1 in 2020. A regression analysis indicated that the maximum DMA at the harvest stage （19.2 t·ha^-1） was obtained at the N application rate of 166.7 kg·ha^-1 （close to 160.0 kg·ha^-1）， and the maximum WUE （37.8 kg·ha^-1·mm^-1） was achieved at the N application rate of 150.0 kg·ha^-1. Based on combined consideration of DMA and WUE， 150-160 kg·ha^-1 can be recommended as a suitable N application range for forage sorghum production in dry regions of the Longdong Loess Plateau.

Effects of nitrogen application on alfalfa yield and quality in China-A Meta-analysis

Min-hua YIN, Yan-lin MA, Yan-xia KANG, Qiong JIA, Guang-ping QI, Jing-hai WANG

2022, 31(9):  36-49.  DOI: 10.11686/cyxb2022127

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Nitrogen plays an important role in the yield accumulation and quality improvement of alfalfa. However， supra-optimal nitrogen application to alfalfa crops not only causes a waste of nitrogen resource， but also aggravates environmental pollution. Additionally， the effect of nitrogen application on alfalfa production varies with different regional conditions and management practices. In this study， we searched the peer-reviewed papers reporting the effects of nitrogen application on alfalfa yield and quality， and quantitatively investigated the effect using meta-analysis. It was found that compared with no nitrogen application， nitrogen application significantly improved the yield and quality of alfalfa， and the mean increase in yield and crude protein content was， respectively， 12.6% （with a confidence interval of 9.0% to 16.2%） and 7.3% （with a confidence interval of 4.1% to 10.6%）， and the mean decrease in acid and neutral detergent fiber contents was， respectively， 5.6% （with a confidence interval of 3.5% to 7.8%） and 3.0% （with a confidence interval of 1.0% to 4.9%）. The effect of nitrogen application of increasing alfalfa yield and crude protein content and decreasing acid and neutral detergent fiber content was more pronounced in Gansu， in regions with an annual average temperature of <8 ℃ and an annual average precipitation of 200-400 mm， when using ammonium nitrate in split dressings with part as base fertilizer and part as top dressing， with irrigation， and with sowing rates of 26 to 30 kg·ha^-1. However， there were differences in yield and quality for suitable nitrogen application rates and planting year. This study can provide a reference for the improvement of alfalfa productivity and the efficient utilization of nitrogen nutrition.

Response of plant leaf ecological stoichiometric characteristics to long-term nitrogen addition in alpine meadow

Guo-hong YOU, Dan LIU, Yan-li WANG, Chang-ting WANG

2022, 31(9):  50-62.  DOI: 10.11686/cyxb2021496

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Nitrogen （N） is critical to plant growth and anthropogenic N addition has been a main source of N input in many terrestrial ecosystems. As an important method for modifying soil nutrient status， N addition affects soil physicochemical properties which in turn affect leaf ecological stoichiometric characteristics. In order to study the effect of N addition on leaf ecological stoichiometric characteristics， we conducted an N fertilization experiment in an alpine meadow on the Qinghai-Tibetan Plateau. The N addition experiment was established in May 2012 with four treatments： 0 （CK）， 10 （N₁₀）， 20 （N₂₀）， 30 （N₃₀） g·m^-2·yr^-1. We collected leaves from grass， sedge， legume and forb in August， 2018， and we measured the leaf carbon （C）， N and phosphorus （P） contents. Data from the four treatments were compared and differences in leaf carbon （LC）， leaf nitrogen （LN）， leaf phosphorus （LP） and their stoichiometric ratio among treatments were identified， and analyses were conducted to determine environmental factors influencing leaf ecological stoichiometric characteristics. It was found that： 1） N addition significantly increased the leaf carbon （LC） content of grass， but significantly decreased the LC content of legume， and LC content of sedge and forb was not significantly changed （P>0.05）. The LN of the four plant functional groups increased markedly with increasing N addition （P<0.05）， but the LP of the four plant functional groups varied inconsistently. 2） In general， the LC/N of the four plant functional groups decreased， while the LN/P and LC/P increased with increasing N addition. 3） Soil moisture content （SMC） was significantly （P<0.05） correlated with plant LC， LN， LP， LC/N， LN/P and LC/P in all cases， and SMC contributed mostly to the variance of the leaf ecological stoichiometry （10.28%， P<0.001）. Compared with grass， sedge and legume， the responses of forb to SMC was relatively sensitive. The LN， LN/P and LC/P of forb decreased but the LC/N and LP of forb increased linearly with SMC. In summary， the responses of the four plant functional groups to N addition differed； SMC was the key factor influencing the change in leaf ecological stoichiometric characteristics of the four plant functional groups N addition.

Effect of nitrogen application on photosynthetic daily variation， leaf morphology and dry matter yield of alfalfa at the early flowering growth stage

Yan-liang SUN, Jun-wei ZHAO, Xuan-shuai LIU, Sheng-yi LI, Chun-hui MA, Xu-zhe WANG, Qian-bing ZHANG

2022, 31(9):  63-75.  DOI: 10.11686/cyxb2021343

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In this research， studies on leaf morphological characteristics and the diurnal changes of photosynthesis in a drip-irrigated alfalfa （Medicago sativa） crop were monitored under different nitrogen levels and the relationships between the daily changes of photosynthesis， leaf morphology， and dry matter yield were analyzed in order to better understand the mechanism of the impact of nitrogen on alfalfa dry matter yield development. The study thus provides a theoretical framework for optimizing the nitrogen management strategy of alfalfa in commercial production. The study used a single factor randomized complete block design with four nitrogen application levels of 0 （CK）， 60 （N₁）， 120 （N₂）， and 180 kg N·ha^-1 （N₃）. At the early flowering growth stage， daily photosynthetic variation， leaf morphology， leaf nitrogen content， and yield components were of the alfalfa were measured. It was found that the net photosynthetic rate， transpiration rate， and water use efficiency of alfalfa leaves under the nitrogen application treatments were higher than those under the non-nitrogen application treatment， and the intercellular CO₂ concentration of alfalfa leaves under the nitrogen application treatments was lower than that under the non-nitrogen application treatment. The environmental factor that had the greatest combined effect on net photosynthetic rate and transpiration rate was photosynthetic effective radiation. The leaf length， leaf width， leaf area， and specific leaf weight of alfalfa， as well as leaf dry weight， stem dry weight， dry matter yield， leaf nitrogen content， starch， and soluble sugar content all showed a pattern of initial increase and then decrease with successive increments of N application. For different nitrogen concentrations， leaf area was the most significant factor affecting leaf morphological structure， followed by leaf specific weight， leaf length， and leaf width. The effects on dry matter yield of alfalfa were， in descending order， leaf nitrogen content>net photosynthetic rate>leaf area>transpiration rate>specific leaf weight. The decrease in photosynthetic rate in the zero-N and high-N treatments was primarily due to the inhibition of photosynthetic activity； This is a non-stomatal factor. Based on a principal component analysis， the highest overall score for dry matter yield， leaf morphology and photosynthesis was obtained in the N₂ treatment， followed by N₃， N₁ and CK treatments. Therefore， nitrogen fertilization promoted the synergistic improvement of photosynthetic rate and photosynthetic area in alfalfa. It facilitated the production of photosynthetic products， thereby increasing alfalfa dry matter yield， especially at the nitrogen application rate of 120 kg·ha^-1.

Effect of water and fertilizer coupling on seed yield and composition of alfalfa grown with underground drip irrigation in Ningxia

Xing WANG, Wei HUANG, Shu-yan YU, Xiao-yun LI, Xue-qin GAO, Bing-zhe FU

2022, 31(9):  76-85.  DOI: 10.11686/cyxb2021380

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This study investigated the most suitable irrigation and fertilizer rates for alfalfa （Medicago sativa） seed yield under drip irrigation in Ningxia. The alfalfa cultivar used in the experiment was ‘Gannong No.4’ and the experiment was laid out in a two-factor split plot design. There were four irrigation rates （900， 1350， 1800 and 2250 m³·ha^-1） in the main plot treatments， and five fertilizer levels （N-P₂O₅-K₂O applied in proportions by weight 0-0-0， 9-45-60， 18-90-120， 27-135-180 and 36-180-240 kg·ha^-1， respectively）. The results showed that appropriate irrigation and fertilizer applications improved alfalfa seed yield. With successive increments in irrigation and fertilizer alfalfa seed yield initially increased and then decreased. Irrigation had a significant effect on the alfalfa floret number， number of inflorescences per plant， number of pods formed， seeds per pod， pod setting rate and thousand seed weight. A path coefficient analysis showed that the number of inflorescences per plant， reproductive branch number， thousand seed weight and pod setting rate had important determinants of the seed yield of alfalfa. Alfalfa seed yield and irrigation water use efficiency were the highest at an irrigation rate of 900 m³·ha^-1 and an N-P₂O₅-K₂O fertilizer rate of 27-135-180 kg·ha^-1. According to a regression optimization model， the optimal irrigation rate for alfalfa seed production in the Ningxia Yellow River irrigation area under local soil conditions was 2250 m³·ha^-1， and the optimal fertilizer amount was 34 kg·ha^-1 of nitrogen fertilizer， 172.68 kg·ha^-1 of phosphate fertilizer and 230.28 kg·ha^-1.

A study of the different cultivation treatments and effects on the sowing process of Fritillaria cirrhosa and Fritillaria unibracteata

Yan-zhu MA, Wen-guang ZHANG, Ran LI, Chun-ya CHENG, Hai-xu WU, Ling JIN, Zhi-jia CUI, Yi MA, Zhen-heng WANG, Yuan-yuan WANG

2022, 31(9):  86-95.  DOI: 10.11686/cyxb2021362

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This research explored the dynamic effects of different sowing methods， different mulches， different seed dressing methods， and different fertilizer treatments on the sowing process of Fritillaria cirrhosa and Fritillaria unibracteata. The number of emerged seedlings of the two Fritillaria species seeds showed a sigmoid curve relationship with time in days since sowing for most treatments with the increase of days after sowing， and the consistency between treatments was significant. There were positive correlations between the seedling emergence rate of F. unibracteata treated with partial fertilization and the number of days after sowing. At （30±3） days after sowing， the final germination percentage for the seedlings of the two Fritillaria species had been reached， and for a given treatment the growth and development of F. cirrhosa seeds was better than F. unibracteata. It was found that drilling was better than broadcasting or ridge sowing； Covering with wheat straw was better than covering with pine needles or plant ash or sheep dung； Sowing without seed dressing was better than dressing with plant ash or sheep manure. The optimal fertilization rates for F. cirrhosa were nitrogen 2.00 g·m^-2， phosphorus 4.90 g·m^-2， potassium 1.25 g·m^-2. The optimal fertilization rates for F. unibracteata were nitrogen nil， phosphorus 9.80 g·m^-2， and potassium 2.50 g·m^-2.

Allelopathic effects of extracts of Sonchus asper on seed germination and seedling growth of three herbaceous flower species

Ying-zi GUO, Wen-qing JIA, Song-lin HE, Zheng WANG

2022, 31(9):  96-106.  DOI: 10.11686/cyxb2021371

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This study explored the allelopathic mechanisms at play in competition between Sonchus asper and common herbaceous flowers. In this experiment， a petri dish bioassay was used to study the effects of different concentrations of extracts from aboveground and underground parts of S. asper on seed germination， seedling growth activities of related enzymes and malondialdehyde （MDA） content of the three herbaceous flower species Orychophragmus violaceus， Dianthus chinensis and Brassica juncea. It was anticipated the results might lay a foundation for development of biological control methods for weeds. It was found that the extracts of S. asper typically had a promotional effect at low concentration and an inhibitory effect at high concentration on the seedling growth of the three tested flower species. At a concentration of 5 g·L^-1， the promotional effect of the two extracts was greatest for O. violaceus， followed by D. chinensis，and the inhibitory effect reached a maximum at a concentration of 100 g·L^-1. The two S. asper extracts increased the activity of superoxide dismutase （SOD） in seedlings of the three tested flower seedlings. For O. violaceus and B. juncea this effect peaked at 50 g·L^-1， and for D. chinensis the effect peaked at 25 g·L^-1， and SOD activity remained higher than control at 100 g·L^-1. The activities of peroxidase （POD） and catalase （CAT） in the tested flower species were increased at low concentrations of S. asper extract and then decreased at higher concentration， while the content of MDA increased with successive increases in the concentration of the extract. There was a very significant positive correlation between POD activity and seed germination rate of D. chinensis， and a highly significant positive correlation between POD activity and stem length and root length in B. juncea. The root length of O. violaceus wassignificantly positively correlated with the activities of POD and CAT， and stem length and the germination rate of O. violaceus wassignificantly positively correlated with the activity of CAT. A calculated index of the overall degree of allelopathic activity of the S. asper extracts on seed germination and growth ranked the effects on the tested flower species B. juncea>D. chinensis>O. violaceus. In summary， the extract causes a degree of damage to cell membranes of the three tested flower seedlings， so it would be advisable to avoid the flower planting in land seriously infested with S. asper.

Effects of Suaeda glauca rhizobacteria and endophytic bacterial strains on alfalfa growth under salt-alkaline stress

Yang-yang MIAO, Yan-rui ZHANG, Biao SONG, Xu-tong LIU, An-qi ZHANG, Jin-ze LV, Hao ZHANG, Xiao-hua ZHANG, Jia-hui OUYANG, Wang LI, Shan-min QU

2022, 31(9):  107-117.  DOI: 10.11686/cyxb2021369

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This research investigated the effects of rhizobacteria and endophytic bacteria strains on alfalfa seedling growth under salt-alkaline stress in alfalfa （Medicago sativa） cultivarLongmu No.801. Rhizobacteria and endophytic bacteria from plants with strong tolerance to salt-alkaline stress were isolated from Suaeda glauca roots （JG1）， rhizosphere soil （JT4） and stems （JJ5） and were inoculated around the roots of alfalfa seedlings. One week after inoculation， neutral salts （NaCl， Na₂SO₄） and alkaline salts （NaHCO₃， Na₂CO₃） were mixed in the proportions NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃ = 9∶1∶1∶9， and the roots of alfalfa seedlings were irrigated with 0， 100， 150， 200 mmol·L^-1 of these salt-alkaline solutions. The effects on the growth and physiological indexes of alfalfa of these inoculations under the four salt concentrations were analyzed by membership function and principal component analysis. It was found that the three growth-promoting bacteria alleviated the inhibitory effects of salt-alkaline stress on alfalfa and promoted alfalfa growth. The growth-promoting effect of the isolated bacterial strains on alfalfa seedlings under salt-alkaline stress was JT4>JG1>JJ5.

Fine root turnover of alfalfa in different soil horizons under different nitrogen and phosphorus levels

Jun-wei ZHAO, Sheng-yi LI, Yan-liang SUN, Xuan-shuai LIU, Chun-hui MA, Qian-bing ZHANG

2022, 31(9):  118-128.  DOI: 10.11686/cyxb2021340

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This research explored the dynamics of fine root turnover and distribution in different soil horizons of alfalfa （Medicago sativa） under different nitrogen and phosphorus application conditions in a field experiment with a two-factor randomized block design in which the relationships between the indexes of fine root turnover were analyzed. Four phosphorus application levels ［0 （P₀）， 50 （P₁）， 100 （P₂） and 150 kg·ha^-1 P₂O₅ equivalent （P₃）］ and two nitrogen application levels ［0 （N₀） and 120 kg·ha^-1 （N₁）］ were included in a total of 8 treatments. The turnover characteristics of fine roots in 0-60 cm soil horizon were monitored through minirhizotron. It was found that： 1） With the same rate of N application， alfalfa standing biomass， root surface area density， and fine root production and death rate were typically maximized at P₁ or P₂， with values for P₂ significantly greater than those for P₀ （P<0.05）. 2） With the rate of P application， values for the N₁ treatment were significantly greater than those for the N₀ treatment （P<0.05）. In different soil horizons， under the same nitrogen application conditions， alfalfa fine root mass in the 0-30 cm soil horizon initially increased and then decreased with successive rises in the rate of P application. In the 0-15 cm soil horizon， alfalfa fine root mass in treatment P₂ was significantly higher than that in other treatments （P<0.05）. In the different treatments， alfalfa fine roots were mainly found in the 15-30 cm soil horizon. Under the same nitrogen application rate， the fine root turnover of alfalfa initially decreased and then increased with successive increases in phosphorus application rate. Among the measured parameters， the fitting effect was best and the correlation coefficient was greatest between fine root death and root turnover. In conclusion， optimal of root mass and root surface area density of alfalfa fine roots were observed in the treatment combination N₁P₂， and this management regime is recommended for the promotion of root turnover and growth in alfalfa.

The effect of last cutting time on the antioxidant system and cold resistance of alfalfa root-neck

Wei-dong CHEN, Yu-xia ZHANG, Qing-xin ZHANG, Ting-yu LIU, Xian-guo WANG, Dong-ru WANG

2022, 31(9):  129-138.  DOI: 10.11686/cyxb2021379

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This research explored the effect of different last cutting time on the cold resistance of alfalfa （Medicago sativa） cultivar ‘Gongnong No.1’ in the Horqin sandy land habitat and the relationship between the last cutting time and changes in the antioxidant system under low temperature stress. The experiment included last cutting times of August 25， September 5， September 15， September 25， October 5， October 15， October 25， and November 5. The crowns were excavated in early winter and subjected to low temperature freezing stress treatments of -10， -15，_c-20， -25， and -30 ℃， with low temperature storage （4 ℃） as the control. Measurements after low temperature storage included the relative electrical conductivity， malondialdehyde （MDA） content， and superoxide dismutase （SOD）， peroxidase （POD） and catalase （CAT） activities. The semi-lethal temperature was calculated from the relative conductivity following a logistic regression equation， and the correlations between the semi-lethal temperature and the antioxidant properties were analyzed. It was found that the semi-lethal temperature for alfalfa last mowed on August 25， September 5， September 15， September 25， October 5， October 15， October 25， and November 5 was， respectively， -18.03， -17.61， -17.03， -16.59， -15.80， -15.82， -16.83， -16.34，_c-17.12 ℃； The semi-lethal temperature of alfalfa root neck and the POD and CAT activities under -10 ℃ low-temperature freezing stress were significantly negatively correlated （P<0.05）； The semi-lethal temperature and SOD activities under -15， -20， and -25 ℃ low temperature stress were significantly or extremely significantly negatively correlated. There was also a significant or very significant positive correlation between semi-lethal temperature and MDA content under low temperature freezing stress of -15， -20， -25， and -30 ℃. For the different last cutting times， the cold resistance of alfalfa ranked uncut>August 25>November 5>September 5>October 15>September 15>October 25>October 5>September 25. The last cutting time regulates the SOD， POD， and CAT enzyme activities in the root neck of alfalfa. An appropriate last cutting time results in lowered active oxygen levels， a reduced degree of membrane lipid peroxidation， and improved cold resistance. Therefore， it is recommended to carry out the last mowing of alfalfa stands before September 5 or after November 5 in the Horqin sandy area.

Effects of exogenous silicon application on physiological parameters， root architecture and diameter distribution of maize under cadmium stress

Ying JIANG, Chang WEI, Qiu-juan JIAO, Feng-min SHEN, Ge-zi LI, Xue-hai ZHANG, Fang YANG, Hai-tao LIU

2022, 31(9):  139-154.  DOI: 10.11686/cyxb2021499

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The aim of this study was to explore the effect of silicon （Si） on the root architecture， root diameter distribution and seedling growth of maize （Zea mays） under cadmium （Cd） stress， and to find an effective way to alleviate the toxicity of Cd on maize seedlings. The experiment had eight treatments： Control （no Cd， no Si）， Cd only and six different concentrations of applied Si （0.25， 0.50， 1.00， 1.50， 2.00 and 4.00 mmol·L^-1 Si） with hydroponic cultivation to test the Cd concentration and content of maize， growth-related indicators， photosynthetic indicators， and root architecture and diameter. The root architecture was assessed by classifying roots into four diameter classes （Ⅰ， <0.5 mm； Ⅱ， 0.5-1.0 mm； Ⅲ， 1.0-1.5 mm； Ⅳ， <1.5 mm） and the plant characteristics of the various treatments were compared. It was found that Cd stress inhibited the growth and development of maize seedlings， the chlorophyll content increased， and the photosynthetic parameters were significantly decreased. Total root length， root surface area， root volume， number of root tips and root forks， including root length of diameter classes Ⅰ-Ⅲ， root surface area and root volume of the diameter classes of Ⅰ-Ⅱ were decreased significantly. After applying different concentrations of Si， the Cd accumulation of plants was reduced by 12.65%-88.07%， and the Cd toxicity was alleviated to varying extents. Alleviation of Cd toxicity manifested as increase in plant height， main root length， biomass and tolerance index. In plants with the 0.25 mmol·L^-1 concentration of Si applied， the total chlorophyll content was increased by 11.76%. Under Cd stress， stomatal conductance， intercellular CO₂ concentration and transpiration rate were significantly increased with the applied Si concentration of 1.00 mmol·L^-1. The total root length， number of root forks， and the root length， root surface area and root volume in the Class Ⅰ diameter range were maximized at the Si concentration of 1.00 mmol·L^-1； The root surface area and root volume peaked at the Si concentration of 1.50 mmol·L^-1. Correlation analysis showed that the total root length and root surface area of roots in diameter classes Ⅰ-Ⅲ， and the root volume of roots in diameter classes Ⅰ-Ⅱ diameter range were significantly negatively correlated with Cd translocation index. Comprehensive evaluation of the effects of different treatment showed that the 1.00 mmol·L^-1 exogenous Si treatment provided the most efficacious alleviation of 50 μmol·L^-1 Cd toxicity in maize. The results showed that Si application reduced the absorption， accumulation and transport of Cd by the roots of maize seedlings， and reduced the concentration and accumulation of Cd in the shoots. These effects reduced the impact of Cd on the photosynthetic system， increased the biomass of maize seedlings， and promoted the distribution of photosynthetic products to the root system， reducing the impact of Cd on root architecture， improving the ability of maize to tolerate Cd， and alleviating its toxic effects.

Characterization and transcriptional regulation analysis of the LpPIL5 gene in perennial ryegrass

Jia-ming YAO, Yue HE, Huan-huan HAO, Xin-ru HUANG, Jing ZHANG, Bin XU

2022, 31(9):  155-167.  DOI: 10.11686/cyxb2021382

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Phytochrome-interacting factors （PIFs）， a subfamily of the bHLH family， play important roles in plant light and hormone signaling， and stress tolerance. In the current study， a PIF gene was cloned from perennial ryegrass （Lolium perenne）， and its genetic sequence was most closely related to Arabidopsis thaliana AtPIF5， therefore， it was named LpPIL5-like （LpPIL5）. The coding region sequence （CDS） of this LpPIL5 gene is 1410 bp， containing 5 exons， encoding 470 amino acids. The protein it codes for has a typical bHLH domain and APB motif and is localized in the nucleus. The promoter region （1500 bp） of LpPIL5 has various cis-elements， including ABRE， MBS， G-box， and others， related to light， hormone， and stress responses. The results of transcription analysis showed that relative expression of LpPIL5 was high in leaves， but low in roots， stems， and leaf sheaths. The transcription of LpPIL5 was also regulated by circadian rhythm， and was significantly higher in light than in dark. In addition， its relative expression levelin leaves was significantly inhibited under polyethylene glycol （PEG）， NaCl， CdCl₂， high temperature stresses， and by N-（phenylmethyl）-9H-purin-6-amine （6-BA） and abscisic acid （ABA） treatments. In roots， the relative expression of the LpPIL5 gene increased significantly after 12 h of these treatments， and became significantly higher than in control plants after 24 h of treatment.

The evolution， characterization and transcriptional responses to multiple stresses of the WRKY genes in Chenopodium quinoa

Li-yuan HOU, Ju-qing JIA, Xiao-dong JIANG, Yu-chuan WANG, Jing ZHAO, Yu-huai CHEN, Sheng-xiong HUANG, Shen-jie WU, Yan-hui DONG

2022, 31(9):  168-182.  DOI: 10.11686/cyxb2021347

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The WRKYs are important plant transcription factors， which regulate growth and development， and responses to various stresses in plants. The aim of the research was to elucidate evolutionary links and explore ways to exploit the stress responsive members of the WRKY gene family in Chenopodium quinoa. Systematic bioinformatics methods were used to identify the genome-wide occurrence of WRKY genes in C. quinoa， determine their chromosomal location， classification and systematic evolutionary affinities， conduct synteny analysis and measure expression profiles under different stresses. In total， 90 WRKY genes were identified in the genome of C. quinoa. These were classified as group Ⅰ （18 members）， group Ⅱ （46） and group Ⅲ （12）. Fourteen WRKY family members could not be assigned to a group due to the lack of WRKYGQK peptide and dramatic variation of the zinc finger. The members of group Ⅱ were further assigned to five subgroups： Ⅱ-a （9）， Ⅱ-b （4）， Ⅱ-c （13）， Ⅱ-d （10） and Ⅱ-e （10）. A compiled phylogenetic tree identified WRKY gene clusters that were consistent with the WRKY gene classification， further supporting the accuracy of our classification of WRKY member genes. Additionally， the protein sequences of WRKY member genes from different groups revealed group-specific conserved domains. The syntenic genomic regions between C. quinoa， Chenopodium pallidicaule and Chenopodium suecicum demonstrated that the WRKY gene expansion in C. quinoa resulted from the whole genome duplication of C. quinoa. Under drought， heat， salt and low P， and groundnut chlorotic fan-spot virus （GCFSV） infection stresses， the expression levels of a number of WRKY genes were significantly down- or up-regulated， implying these WRKY genes participate in regulating the responses to these biotic and abiotic stresses. Our results indicate good gene candidates and provide reference information for future studies of stress tolerance in C. quinoa.

Assessment of genetic structure of 3 Maiwa yak preserved populations based on genotyping-by-sequencing technology

Shi-long MA, Xiao-wei LI, Xiang LI, Shu-qiong XIE, Yi-li LIU, Jiao TANG, Ming-feng JIANG

2022, 31(9):  183-194.  DOI: 10.11686/cyxb2021464

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The Maiwa yak， a breed of domestic yak， is an excellent yak strain for meat and milk production on the Qinghai-Tibetan Plateau. This study explored the genetic diversity and genetic structure of the Maiwa yak population in Longri Breeding Farm in Sichuan Province. A key aim was to identify genes important to defining germplasm categories and thereby evaluate the conservation status of three preserved populations. We used genotyping-by-sequencing （GBS） technology to categorize three preserved populations： The ‘pink mouth’ population （FZ） （n=140）， the ‘full black’ population （QH） （n=211） and the ‘gray coat’ population （FL） （n=55）. Analysis of the resulting sequences identified 126122 single nucleotide polymorphism （SNP） markers which were used to calculate genetic statistics such as observed heterozygosity （Ho）， inbreeding coefficients （Fis）， genetic differentiation index （Fst）， and genetic distance （DR）. The average observed heterozygosity values and average expected heterozygosity values （He） of the whole Maiwa yak population were 0.3038 and 0.3036. The genetic diversity of Maiwa yak was high. The Ho values of QH， FZ and FL were 0.3029， 0.3042， 0.3044， respectively， while the Fis values were 0.0144， 0.0152， 0.0209， respectively. The intensity of artificial selection of FL and FZ was greater than QH， and the lower inbreeding level showed that the conservation status of the three preserved populations was better in Longri Breeding Farm. Structure analysis showed that the pedigree of some individuals in QH and FL is pure， while the pedigree of other individuals is extremely mixed. The Fst and DR of FZ and QH populations were 0.03513 and 0.0358， respectively. The genetic distance between FZ and QH was the greatest and there was obvious genetic differentiation between them； This result was consistent with a constructed phylogenetic tree. In addition， we also performed a selective signal analysis of the three preserved populations using Fst and π methods. The 104 selected genes were involved in a wide range of metabolic processes， including reproductive function， the immune system， embryonic development， lipid metabolism and others， as well as signal transduction， reproductive hormone， endocrine/exocrine， and other signal transduction pathways. Some of them， such as PPP3CC， KCNMA1， ROCK2， GNAQ， MEF2C， and KIT geneswere related to reproduction， meat quality， coat color traits and stress response of Maiwa yaks. In conclusion， the existing conservation strategy of Maiwa yak is tenable. The study provide genetic reference data for future conservation breeding and genetic improvement of Maiwa yak.

Effects of fermented Hypsizygus marmoreus mushroom residue on slaughter performance and mutton quality of goats

Yao ZHANG, Xiao-yun HUANG, Xin-zhu CHEN, Qin-lou HUANG, Xiu-sheng HUANG, Hai-dong HAN

2022, 31(9):  195-205.  DOI: 10.11686/cyxb2021320

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This experiment was to study the effects of adding different ratios of fermented Hypsizygus marmoreus mushroom residue to a standard feed， on the slaughter performance， and meat amino acid and fatty acid content of Jianyang big ear goats. A single factor experiment design was chosen， and 48 Jianyang big ear goats were selected and randomly divided into 4 groups with 12 goats in each group. The treatments comprised addition of zero （group C， control group）； 20% （group L）， 30% （group M）， and 40% （group H） fermented H. marmoreus mushroom residue to the basic diet. The pre-test diet adaptation period was 10 days， and the trial period was 120 days. It was found that： 1） The pre-slaughter live weight and the eye muscle areas of group L were significantly higher than in group H （P<0.05）； While the weights of lung， kidney， rumen， small intestine， large intestine， and the ratio of the rumen weight to the pre-slaughter live weight were significantly higher than in the other three groups （P<0.05）. The eye muscle area and the weights of lungs， kidneys， rumen， small intestine and large intestine showed secondary changes proportional to the added amount of fermented mushroom residue （P<0.05）. 2） There was no significant difference in the meat pH among the groups （P>0.05）. The 24 and 48 h drip loss of group L was significantly lower than other groups （P<0.05）， and there were secondary changes proportional to the level of addition of mushroom residue in that the yield of cooked meat rate was significantly higher than in group H （P<0.05） while the shear force was significantly lower than in group H （P<0.05）. 3） The total amount of essential amino acids in the longissimus dorsi muscle in group L was significantly higher than in group C （P<0.05）， and the contents of aspartic acid， threonine， leucine， lysine， and arginine were significantly higher than in groups C and H （P<0.05）. The contents of alanine， valine and isoleucine in group L were significantly higher than other groups （P<0.05）， and the contents of proline and glycine were significantly higher than in groups C and M （P<0.05）. Among four groups， the contents of valine， isoleucine， lysine and aspartic acid showed secondary changes proportional to the level of mushroom residue addition （P<0.05）. 4） There were no significant differences in fatty acid content among the groups （P>0.05）. Along the addition gradient， the contents of C18：0 and C18：3n3 fatty acids showed either quadratic change or linear increase in proportion to the level of addition （P<0.05）. The content of C18：3n3 in group H was increased by 16.48% compared with group C. The contents of polyunsaturated fatty acids （PUFA） and n-3 PUFA in the test groups increased to some extent， compared with group C. The n-6/n-3 decreased by 0.64%， 11.73% and 12.34%， respectively for groups L， M and H， compared with group C. To sum up， supplementation of a standard diet with 20% fermented H. marmoreus mushroom residue improved internal organ development and meat quality of goats.

Recent advances in understanding the ecosystem functioning of diverse forage mixtures

Ce YANG, Yu-xue ZHANG, He ZHANG, Chun-yan ZHENG, Feng ZHU

2022, 31(9):  206-219.  DOI: 10.11686/cyxb2021341

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Use of forage mixtures is one of the important planting practices in establishment of intensively managed artificial grasslands to enhance productivity and quality. Understanding the mechanisms underlying species interactions， and exploration of the ecosystem functions and services are essential to management for stable production and sustainability. Here， based on the recent advances in this topic， we discuss how mixed forage systems affect the outcome of interspecific complementarity and competition in above- and below-ground compartments. Next， we address the effects of mixed-species forage sowings on pasture productivity and quality， recourse utilization， biodiversity of soil food webs， and ecosystem stability. Finally， we emphasize the future challenges for selection of suitable plant species with synergistic properties. Longer-term studies are needed to conclusively demonstrate environmental and production benefits of high-diversity forages.

Legal process and governance of public rangelands： Experiences and implications from America

Feng HAN, Zhi-tao ZHANG, Xin ZHANG, Jian-hao WANG, Hao WANG

2022, 31(9):  220-232.  DOI: 10.11686/cyxb2021115

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This paper clarifies the process of legal management of public rangelands in the United States through a literature review， with coverage divided into four categories according to the legislation： Grassland degradation， establishment of multi-utilization and federal ownership， adjustment of the grazing fee system， and amendment of legislation and improvement of policies. Our report details the contradictions and conflicts， governance goals and policy tools of each stage， and summarizes the outcomes. The study found that after experiencing severe degradation of rangelands， the federal government established the principle of multi-utilization under federal ownership through legislation. In the process of legislation， classification， a grazing fee system， public ownership， land resource survey and marketization became more sophisticated， forming a stable governance pattern. From the perspective of a modern property rights system， the public ownership of rangelands is also an effective form of exploration of property rights management for capitalist private ownership countries， and a relatively comprehensive legal system has been formed. Although China and the United States embrace different political and economic systems， especially the property rights structures， the United States example still provides a wealth of experience. It is recommended that China continue to adhere to the principle of state-owned property for grasslands， and strengthen the legal framework for grassland ecological environmental protection and inventory of grassland resources， implement clear classification and management of production and responsibility， and carry out ecological and well-being monitoring. Compensation for grassland ecological outcomes should be incorporated into routine legislation， giving more attention to the supply of products and ecosystem services.