Table of Content

20 November 2022, Volume 31 Issue 11

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Temporal and spatial variation in grassland ground surface soil heat flux on the Qinghai-Tibetan Plateau from 2003 to 2018

Ying LI, Jing WU, Chun-bin LI, Ge-xia QIN

2022, 31(11):  1-14.  DOI: 10.11686/cyxb2022059

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Based on measured data from 7 stations on the Qinghai-Tibetan Plateau， the ground surface soil heat flux （G₀） was calculated， and the diurnal and seasonal variations were analyzed. Combining this data with a MODIS， 1 km resolution all-weather surface temperature data set for Western China and a China regional surface meteorological element driven data set， the Ma model was used to retrieve the ground surface soil heat flux of Qinghai-Tibetan Plateau from 2003 to 2018， and the differences in surface soil heat fluxes of different grassland types were analyzed. It was found that： 1） The soil heat flux G₀ in the surface layer was greater than that in the subsurface layers. The diurnal curve of G₀ showed an inverted “U” shape， and the flux was relatively gentle at night compared with that during the day. 2） The seasonal amplitude of soil heat flux， G₀ in the surface layer ranked summer>spring>autumn>winter. The average value of G₀ in spring and summer was typically positive， while the average value of G₀ in autumn and winter was basically negative. The ground surface soil heat flux in the northwest of the plateau in summer is higher than that in the southeast， while the opposite occurs in winter. 3） The soil heat flux of plateau grassland ranged between 40 and 80 W·m^-2. The highest average value of G₀ among all categories of grassland in the 16 years surveyed was 76.557 W·m^-2 for the ‘desertification’ category of temperate grassland， and the lowest was 46.118 W·m^-2 for the alpine meadow category. 4） The G₀ of plateau grassland increased and then decreased through any one calendar year and seasonally was ranked summer>spring>autumn>winter. The lowest G₀ in spring and summer occurred in alpine meadow， while the highest in spring was in ‘desertification’ temperate grassland and the highest in summer was in the temperate grassland category； The highest G₀ in autumn and winter was in the warm shrub grassland， while the lowest was in the alpine deserts steppe. The above results can provide reference data for the study of surface energy balance of plateau grassland.

Effects of slope on soil properties and post construction desertification of highway embankments in an Alpine Meadow region

Bi-hua GUO, Xue-mei ZHANG, Jin-ping LIU, Ming-hong YOU, Xiao-hong GAN, Yong YANG

2022, 31(11):  15-24.  DOI: 10.11686/cyxb2021460

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This research investigated effect of slope on the performance of highway embankment soil properties post construction， as there is a demand for technical data of this nature to underpin the design of highway revetment work in alpine meadow regions of China. A section of national road G248 in Northwest Sichuan Alpine Grassland， built 10 years ago， was identified as a study site and plots were marked out for sampling on five slope classes： gentle slope， 6°-15° （GS）； moderate slope， 16°-25° （MS）； steep slope， 26°-35° （SS）； very steep slope， 36°-45° （VS）； extreme slope， >45° （ES）. Undisturbed flat natural grassland >10 m distant from the roadbed was used as the control （CK）. Measurements conducted included determination of particle size composition， physical and chemical parameters of the soils， vegetation cover and the proportion of the plot area exhibiting degradation or desertification. The relative reduction rate of organic matter and total nitrogen was also determined， and differences in soil water content and fertilizer retention capacity were assessed. It was anticipated these data would provide a basis for the construction of ecologically sound slope protection structures in alpine regions. It was found that： 1） Increased slope significantly decreased the proportion of clay and silt particles and increased the proportion of coarse sand and small stones （P<0.05）. The greater the slope， the greater the soil bulk density and pH value， and the lower the soil water content. 2） Slope facilitated leaching of soil carbon fractions with the leaching intensity of the fractions ranking soil organic matter （SOM）>total carbon （TC）>inorganic carbon （IC）>dissolved organic carbon （DOC）. For example， SOM levels were， respectively， 115， 92， 72， 30， 9 and 3 mg·kg^-1 for CK， GS， MS， SS， VS， and ES slope classes while DOC levels ranged from 35.4 mg·kg^-1 in CK to 9.2 mg·kg^-1 in ES. 3） The ranking for the effects of slope on various soil fertility measures was： effective N>alkali-hydrolysable N>total N>available K>available P>total K>total P. Thus， available N was more easily lost than total N and alkali-hydrolysable N. Available N levels declined progressively across slope classes from 236 mg·kg^-1 in CK to 6.3 mg·kg^-1 in ES， while total N and alkali-hydrolysable N showed marked loss between GS and VS slope classes. A slope threshold for sharp increase in loss of total P and available P was observed between GS and MS slope classes. With increase in slope gradient， the total K increased， while the available K content decreased. 4） With respect to the influence of slope on the degree of desertification： for CK and GS >90% of the plot area was classed as non-desertified； for GS 79% of the plot area was moderately or severely desertified； for SS， VS and ES， 79， 86 and 94%， respectively， of the plot area was severely or extremely severely desertified. The proportion of severe desertification increased markedly at >15° slope （i.e. MS） and the proportion of extremely severe desertification increased markedly at >25° slope （i.e. SS）. 5） When the slope effects were expressed in relative terms， the relative increase in desertification was high and changed little at slopes >15°， while the relative decreases in organic matter and total nitrogen were high and changed little once slope exceeded 25°. As slope angle increased， relatively low rate of total coverage percentage and powder particles <0.02 mm and the relative increase rate of sand particles >0.05 mm increase significantly. In summary， as slope of the study plots increased， fine sand， silt and clay particles were progressively lost， soil fertility progressively declined， and the degree of desertification increased markedly. Therefore， the technical plan for ecologically sound slope protection in highway construction should be formulated according to the steepness of the slope.

Effects of plateau pika on the relationship between plant species diversity and functional diversity in alpine meadow

Yuan-yuan DUAN, Jing ZHANG, Ling-ling WANG, Cai-feng LIU, Yi-mo WANG, Su ZHOU, Zheng-gang GUO

2022, 31(11):  25-35.  DOI: 10.11686/cyxb2021444

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The relationship between plant species diversity and functional diversity in grassland will change with environmental changes. The plateau pika （Ochotona curzoniae） has an effect on the hydrothermal process of alpine meadow in its nesting area. However， it is not clear whether the disturbance of plateau pika effects the relationship between plant species diversity and functional diversity in alpine meadow. A random stratified and paired design was used to select plots in Luqu county in Gansu Province， and Qilian and Gonghe Counties in Qinghai Province and a field survey was conducted to investigate the effects of plateau pika disturbance on the relationship between plant species diversity and functional diversity of the alpine meadow. It was found that plateau pika disturbance significantly increased the plant species richness index and the species diversity index but did not significantly affect the species evenness index. Plateau pika disturbance significantly increased plant functional richness index （P<0.05） but had no significant effect on the plant functional evenness index or the functional divergence index. With plateau pika disturbance effects， the relationship between plant functional richness index and species richness index changed from a logarithmic function to a quadratic function， and the relationship between plant functional evenness index and species evenness index changed from non-significant to significantly positive. In addition， positive correlations between functional richness index and species richness index， and functional richness index and species diversity index were significantly decreased， as were negative correlations between functional divergence index and species richness index， and functional divergence index and species diversity index were significantly decreased. The findings of this study provide basic information for understanding the mechanism of species coexistence of plant communities under plateau pika disturbance and help understanding of how plant diversity effects in an alpine meadow ecosystem function under plateau pika disturbance.

Harmful and economic thresholds for rodent pests in the Alxa desert area under different grassland utilization patterns

Ke YANG, Shuai YUAN, Xiao-dong WU, Hao-ting ZHANG, Shan-shan SUN, He-ping FU, Yong-quan ZHAO, Shu-yan WANG, Qi-fu LIU

2022, 31(11):  36-47.  DOI: 10.11686/cyxb2021429

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The rodent damage threshold and the rodent economic threshold are indicators that must be clearly defined in the practice of grassland rodent prevention and control. Different grassland types or different utilization methods of the same grassland type have completely different values for these two indicators. The damage threshold is the population density of pests at which the grassland is obviously compromised， and the economic threshold is the population density at which further pest population increases will cause economic losses. The Alxa desert region is ecologically fragile， and rodents are endemic. This study selected continuous grazing areas and prohibited grazing areas in the desert area of Alxa Left Banner and from 2015 to 2019 to investigated the species and density of pests using the ‘mark and recapture’ method， together with sampling to investigate the aboveground plant biomass in the sample area in August. The measured rodent unit densities and their daily food intakes were used to estimate the amount of forage loss， and a regression equation was used to obtain a fitted relationship between the rodent density and the ratio of forage loss. It was found that： 1） The fitted curves for the ratio of pest density and forage loss in the continuous and prohibited grazing areas took the form of logistic three-parameter， S-shaped curves. 2） According to the regression equation， the damage threshold in continuous grazing areas was 26 standard rodent units·ha^-1 and the economic threshold was 39.3 standard rodent units·ha^-1. In prohibited grazing areas， the damage threshold was 33.2 standard rodent units·ha^-1 and the economic threshold was 30.2 standard rodent units·ha^-1. Thus， the economic threshold pest density of continuous grazing areas was slightly higher than that of prohibiting grazing areas.

Genetic diversity analysis and fingerprint construction of Elymus germplasm based on SCoT markers

Jing PAN, Jun-chao ZHANG, You-jun CHEN, Qing-ping ZHOU

2022, 31(11):  48-60.  DOI: 10.11686/cyxb2022137

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In this study， SCoT molecular markers were used to analyze the genetic diversity and construct DNA fingerprints of three species of Elymus on the Qinghai-Tibet Plateau to provide a theoretical basis for identification of the different species in collection material. Among 80 SCoT primers， 22 primers were selected for PCR amplification， and a total of 290 bands were amplified， of which 254 were polymorphic with the percentage of polymorphic bands （PPB） of 87.59%. The average values of the Shannon diversity information index （I）， Nei’s gene diversity index （H）， the observed number of alleles （Na）， and an effective number of alleles （Ne） were 0.5411， 0.3643， 1.9856， and 1.6270， respectively. Cluster analysis results showed that the genetic similarity coefficient ranged from 0.50 to 0.80. At a genetic similarity coefficient of 0.53， 46 collections could be divided into 2 groups， and the results of the principal coordinate analysis were consistent with those of cluster analysis. At the same time， the DNA fingerprints of 46 materials were constructed by using 4 SCoT primers. The SCoT molecular marker was suitable for genetic diversity analysis and DNA fingerprint construction of Elymus germplasm resources. This study provides fundamental information for germplasm identification， high-quality character mining， and breeding practice for wild Elymus.

Genetic diversity analysis and comprehensive evaluation of octoploid Tritipyrum-derived wheat breeding lines based on agronomic traits

Li-fang CHANG, Xin LI, Hui-juan GUO, Lin-yi QIAO, Shu-wei ZHANG, Fang CHEN, Zhi-jian CHANG, Xiao-jun ZHANG

2022, 31(11):  61-74.  DOI: 10.11686/cyxb2022004

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Being potential tertiary gene pools， perennial wheatgrasses （Thinopyrum spp.） are recognized sources of genetic variation for wheat （Triticum aestivum） improvement， and wheat-Thinopyrum amphiploids and their derived germplasm have played an important role in increasing the amount of genetic diversity and improving resilience to biotic stress in wheat. In this research， a total of 163 octoploid Tritipyrum-derived breeding lines were evaluated for phenotypic genetic diversity of 13 agronomic traits through diversity analysis， correlation analysis， cluster analysis， principal component analysis and comprehensive multivariate evaluation. It was found that the diversity indexes of five descriptive quality traits ranged from 0.26 to 1.00， with the plant type having the highest diversity. The variation coefficients of 8 yield-related traits ranged from 4.44% to 20.11%， with yield per plant having the highest variation coefficient （20.11%）， followed by effective tiller number （17.37%） and the thousand kernel weight （17.13%）， and with the heading period having the minimum value （4.44%）. The diversity index of measured traits ranged from 1.97 to 2.09， with thousand kernel weight being highest （H'=2.09）， followed by spikelets per spike （H'=2.07）， and the heading date lowest （H'=1.97）. Correlation analysis indicated that the 8 yield-related traits were significantly correlated with each other at the 0.05 or 0.01 probability levels. Systematic cluster analysis based on Euclidean distance of the eight measured yield-related traits demonstrated that the 163 lines were divided into six groups with significant difference among them. Each group had its unique characteristics， and groups I and Ⅲ had favorable yield-related traits therefore represented superior germplasm for yield traits. On principal component analysis， the first four principal components represented 81.12% of the genetic information of the 163 surveyed derived lines， among which thousand kernel weight， spikelet number per spike， spike length， and plant height contributed the most and had a positive contribution to yield improvement. In comprehensive multivariate evaluation of phenotypic traits， based on the D value， the five highest scoring germplasm lines （CH16353， CH1742， CH16370， CH16385 and CH16382） with high thousand kernel weight were screened out for wheat breeding. This study showed that the octoploid Tritipyrum-derived breeding lines are rich in genetic diversity for yield-related traits， and could provide valuable reference for wheatgrass-derived germplasm used in wheat breeding programs.

Effects of dietary neutral detergent fiber on muscle fiber type composition and meat quality characteristics of black Tibetan sheep

Li ZHOU, Zhi-you WANG, Bao-chun YANG, Sheng-zhen HOU, Feng-shuo ZHANG, Lin-sheng GUI

2022, 31(11):  75-85.  DOI: 10.11686/cyxb2021439

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The effects of different neutral detergent fiber （NDF） diets on body size indexes， muscle fiber type and meat quality of Qinghai black Tibetan sheep were investigated. Forty healthy 2-month-old black Tibetan sheep with similar body weights ［（10.28±0.43 kg］ were randomly divided into 2 groups with 20 rams per group. They were fed diets with differing neutral detergent fiber （NDF） levels of 26.33% （group L） and 46.14% （group H）. Using enzyme-linked immunosorbent assay， ATPase histochemical stain and real-time PCR， the muscle fiber characteristics， gene expression of myosin heavy chains （MyHCs） and meat quality in Black Tibetan sheep were evaluated. Results were as follows： 1） The tagma indexes in group H were significantly lower than those in group L （P<0.05）. 2） The number of type Ⅱa muscle fibers in group H was significantly more than in group L （P<0.05）， and the areas of type Ⅰ and type Ⅱa muscle fibers in group H were also greater than in group L （P<0.05）.3） The mRNA expression levels of MyHC Ⅰ and MyHC Ⅱa in group L were lower than those in group H （P<0.05）， but the mRNA expression levels of MyHC Ⅱb and MyHC Ⅱx exhibited an opposite movement （P<0.05）. 4） Compared with group L， superoxide dismutase， glutathione peroxidase， catalase and total antioxidant capacity contents increased （P>0.05） in group H， while the malondialdehyde （MDA） content was significantly decreased with in group L. 5） The muscle shear force in Group L was higher than that in Group H （P<0.05）， while the redness （a^*） was lower than that in Group H （P>0.05）. In conclusion， compared with a low-NDF diet， the high-NDF diet effectively reduced the proportion of glycolic muscle fiber and also enhanced antioxidant capacity， improving the muscle quality of black Tibetan sheep.

Effects of fermented soybean residues on growth performance， apparent nutrient digestibility， meat quality and serum biochemical indexes of Hu sheep

Yang FAN, Wei-biao QI, Chong-miao ZHU, Yu-yang YIN, Sheng-yong MAO

2022, 31(11):  86-93.  DOI: 10.11686/cyxb2021420

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The experiment was conducted to study the effects of fermented soybean residues on growth performance， apparent nutrient digestibility， meat quality and blood physiological indexes of Hu sheep， and to investigate the value of fermented soybean residues in the production of meat sheep. In the present study， twenty-one healthy male Hu sheep with similar body weight were selected and randomly allocated into a basal diet （control） group， a soybean residue group （basal diet+20% soybean residue， SR） or a fermented soybean residues group （basal diet+20% fermented soybean residues， FSR）， with 7 animals in each group. The experiment lasted for 49 days， including a 7-day adaptation period. The results were as follows： 1） Compared with the control and SR groups， addition of 20% fermented soybean residues in the diet （FSR） significantly increased the average daily weight gain of Hu sheep （P<0.05） and significantly reduced the weight gain cost （P<0.05）. 2） The apparent digestibility of dry matter （DM）， crude protein （CP） and neutral detergent fiber （NDF） of Hu sheep in the fermented soybean residues group was significantly higher than that in other groups （P<0.05）. 3） Compared with the SR group， the carcass weight of the FSR group was increased （P<0.05）， while the dressing percentage， meat redness values of the FSR group were greater than those of the other groups （P<0.05）， and the drip loss was lower than other groups （P<0.05）. 4） Compared with the control and SR groups， the serum total protein content of the FSR group was increased （P<0.05）， and the urea nitrogen content was reduced （P<0.05）. Compared with the SR group， the serum albumin content of the FSR group was increased significantly （P<0.05）. In conclusion， the addition of fermented soybean residues in the diet significantly improved the average daily gain of Hu sheep， reduced the feed cost， improved the apparent digestibility of DM， CP and NDF， and improved the meat quality and serum biochemical indexes.

The influences of reseeding date and mowing prior to reseeding on establishment of alfalfa in Leymus chinensis meadows

Qiang LI, Shan CONG, Cheng-zhen ZHAO, Ying-xin HUANG, Dao-wei ZHOU

2022, 31(11):  94-104.  DOI: 10.11686/cyxb2021443

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This research studied the effects of sowing date and cutting prior to sowing on establishment of the leguminous forage， alfalfa （Medicago sativa）， in a lightly degraded Leymus chinensis meadow and investigated the sowing date×cutting interaction. The factorial experiment comprised four sowing dates （May 1， June 1， July 1， August 1） and cutting treatment （cut or uncut） prior to sowing， and evaluated the establishment performance of alfalfa and the ecological mechanisms related to establishment. It was found that soil moisture during emergence of alfalfa was the greatest when sowing occurred on July 1， and clipping prior to sowing significantly decreased the plant height of L. chinensis during emergence and seedling growth of alfalfa. There was a significant sowing date×cutting interaction effect on alfalfa establishment. Clipping prior to sowing significantly increased the emergence percentage of alfalfa through reducing the plant height of L. chinensis and associated above-and below-ground competition， and the seasonal soil moisture change resulted in a 20% higher （P<0.05） alfalfa emergence rate when sowing occurred on July 1. With cutting， the number of surviving alfalfa seedlings and seedling survival rate were greatest （83 plants·m^-2 and 53%， respectively） when sowing occurred on July 1. For later sowing， owing to the shortened growing time， the development and overwintering survival rates of alfalfa seedlings were significantly reduced. Cutting prior to sowing significantly increased the overwintering rate of alfalfa seedlings through improving their development. In the cutting treatment， the number of overwintered alfalfa seedlings （22 plants·m^-2） when sowing was on July 1 was significantly higher than for other reseeding dates. In the second year， a botanical composition measurement showed that clipping prior to reseeding significantly increased the alfalfa biomass within the meadow， and the alfalfa biomass was significantly greater than in other treatments when sowing occurred on July 1 after cutting. Cutting prior to sowing also significantly increased the crude protein content of forage. Based on these research results， normal production practice should include cutting when alfalfa is sown into L. chinensis meadow. Combined with cutting， a sowing date around July 1 is the most favorable for the establishment of alfalfa.

An evaluation of suitability of ten Trifolium repens varieties for use on the Chengdu Plain

Chong-yang HAN, Shuan WANG, Su-tian ZUO, San-bo YAN, Yang WANG, Jia-bang CAI, Cong-yu MA, Xin-quan ZHANG, Gang NIE

2022, 31(11):  105-117.  DOI: 10.11686/cyxb2021417

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The aim of this research was to identify high-quality white clover varieties suitable for planting on the Chengdu Plain. The production traits of 10 white clover varieties were evaluated through the growing season， including hay yield， plant height， stolon diameter， leaf area and other indexes， and the nutritional quality of the tested white clover varieties was determined. It was found that the growth period of the introduced variety ‘Jumbo’ was 306 days， and Jumbo was a late-maturing variety. The growth rate of white clover varieties was the fastest （0.52-0.67 cm·d^-1） after the first cut. After the second and third cuts the growth rate slowed and was lowest （0.34-0.50 cm·d^-1） after the third cut. Among all varieties， ‘Rampart’ had the highest annual hay yield of 14436.44 kg·ha^-1 which was， respectively， 20.0% and 26.7% higher （P<0.05） than that of the control varieties ‘Haifa’ and ‘Huia’. The average hay yield of variety ‘OMK’ was 8898.64 kg·ha^-1， significantly lower than that of the two control varieties （P<0.05）. The natural plant height and ‘stretched height’ of the white clover varieties ranged from 22.6 to 30.2 cm and 35.4 to 53.7 cm， respectively. The variety ‘Rampart’ had the largest leaf area， stem internodes and the greatest stolon diameter. The flowering stem length of ‘Super Huia’， the petiole length of ‘Jumbo’ and petiole diameter of ‘Haifa’ were in each case the best among the white clover varieties tested. The varieties showed great differences in nutritive value measures， and the crude protein content of ‘Ranger’ ranged up to 22.8%. The hay yield and related agronomic traits of 10 white clover varieties were compared and analyzed by grey relational analysis， which showed that the varieties ‘Rampart’， ‘Super Huia’ and ‘Jumbo’ had superior field traits and can be recommended as suitable for planting on the Chengdu Plain.

Effects of nitrogen forms on growth and nitrogen assimilation and utilization of Buchloe dactyloides

Bo-kun ZOU, Xin-ming WANG, Zhang-shan CHU, Xin-hui HUANG, Yu-feng CHEN, Yong-qiang QIAN

2022, 31(11):  118-127.  DOI: 10.11686/cyxb2022025

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This research explored the nitrogen （N） uptake preference of Buchloe dactyloides， in order to improve the management of this species over the whole growth cycle. The experiment included two cultivars of B. dactyloides （‘Sundancer’ and ‘Texoka’） and four different N regimes （N₀： No N as the control， N₁： Urea， N₂： Nitrate N， N₃： Ammonium N and N₄： a 1∶1 mixture of nitrate N and ammonium N）. The rate of N applied was 500 mg N·kg soil^–1 in each case. It was found that total N content， root nitrate reductase （NR） activity， glutamine synthetase （GS） activity and shoot glutamate synthase （GOGAT） activity of B. dactyloides were significantly improved by adding mixed N （P<0.05）. Shoot nitrate N content of B. dactyloides was significantly improved by adding nitrate N （P<0.05）. Root nitrate N and ammonium N contents of B. dactyloides were significantly improved by adding urea （P<0.05）. The shoot ammonium N content and NR activity of B. dactyloides were significantly improved by adding ammonium N （P<0.05）. Shoot GS activity of B. dactyloides was significantly reduced by adding ammonium N （P<0.05）. Root GOGAT activity of B. dactyloides was significantly reduced by adding nitrate N （P<0.05）. Mixed N can better improve the physiological activity and promote the growth of B. dactyloides， but single nitrogen source will inhibit some nitrogen assimilase activity. Based on these results， it is recommended that 1∶1 mixed nitrogen should be used as the nitrogen source in the production of B. dactyloides. Where the ammonium∶nitrate is not 1∶1， urea should be used as the nitrogen source.

Effects of a ridge-furrow rainfall harvesting system on the growth， development and quality of flue-cured tobacco

Ke-ling CHEN, De-quan WANG, Yang LIU, Yi WANG, Yu-hai DU, Chuan-yin DU, Xing-hua MA

2022, 31(11):  128-138.  DOI: 10.11686/cyxb2021461

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The effects of a ridge-furrow rainfall harvesting system （RFRHS） on the growth， development， and quality of flue-cured tobacco were studied to develop a cultivation method for water storage and moisture preservation in the Shandong tobacco cultivation region. Two field experiments were carried out in the same year at different locations using the main local flue-cured tobacco varieties， Yunyan 87 and Zhongyan 100. The soil moisture content， agronomic traits， photosynthetic rate， dry matter accumulation， nitrogen content， nitrogen accumulation， chemical composition， and sensory quality of tobacco leaves were determined. It was found that， in comparison with the conventional cultivation method， the RFRHS increased the soil water content in the 20-60 cm soil layer. This system significantly increased leaf length and leaf width of Yunyan 87 at the budding stage and of leaf area at both budding and flat top crop growth stages. The RFRHS also increased the photosynthetic rate by 28.5% at the flat top growth stage. In addition， the dry matter accumulation， leaf nitrogen content， nitrogen accumulation， total nitrogen and total potassium contents were increased by RFRHS， while the total sugar and reducing sugar contents were decreased when compared with the conventional cultivation method in Yunyan 87. The RFRHS significantly increased the leaf length and leaf area of Zhongyan 100 at the budding stage， increased photosynthetic rate by 14.8% at the flat top stage， increased dry matter accumulation in the vigorous growth stage and nitrogen accumulation in the mature stage. The total alkaloid content in Zhongyan 100 was reduced by 12.7% by RFRHS compared with conventional cultivation but other chemical components were little affected. The RFRHS modified the soil moisture by making full use of rainwater and thus promoted the growth and development of flue-cured tobacco， improved the aroma， after-taste and reduced offensive odor， and improved the sensory quality of both varieties. In summary， the ridge-furrow rainfall harvesting system is a highly efficient， crop quality-enhancing cultivation method for the hilly and mountainous tobacco cultivation area in Shandong Province.

Effects of heavy metal Cu and Pb stress on the growth and physiological characteristics of Galega orientalis seedlings

Hai-ting MU, Ying-zhe WANG, Yi-fan MIAO, Wei-jie YU, Bo XU

2022, 31(11):  139-146.  DOI: 10.11686/cyxb2021463

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This research studied the effects of stress from elevated soil Cu and Pb on seedling growth and physiological characteristics of Galega orientalis. The experiment was a pot trial with plants grown in an artificial soil made up of humus， perlite and vermiculite mixed 4∶1∶1 and treatments included a control （CK） and four concentrations of Cu and Pb stress （240， 360， 480 or 600 mg·kg^–1 applied with irrigation water）. Measurements of seedling shoot and root length and fresh weight were made at 7 and 15 days and physiological indices such as shoot malondialdehyde， proline and soluble sugar and protein levels and peroxidase activity were measured at 21 days. It was found that the shoot length， root length， shoot fresh weight and root fresh weight of G. orientalis showed a pattern of overall increase compared to CK at the lower two Cu and Pb concentrations and shorter stress exposure time， but with increased stressor concentration and exposure duration， root length was decreased by 23.60% compared with CK at the treatment concentration of 600 mg Pb·kg^–1 and 15 days of Pb exposure. Proline and peroxidase levels in G. orientalis exhibited an overall pattern of constant increase with increase in stressor concentration. With increase in Pb concentration， the malondialdehyde content in plants increased with Pb concentration up to an exposure level of 480 mg Pb·kg^–1， but showed a significant decrease at 600 mg Pb·kg^–1， while under stress from Cu exposure the malondialdehyde content showed a pattern of continuing increase with increase in Cu concentration. The soluble sugar content initially increased and then decreased with increasing Pb concentration while at Cu concentrations of 240 and 360 mg Cu·kg^–1， the soluble sugar content of G. orientalis was lower than for CK plants. The soluble protein content was decreased at lower levels of Pb stress， but at the treatment concentration of 600 mg Pb·kg^–1 was increased by 78.35%， compared to CK. Under Cu treatment， the soluble protein content of the plants showed a pattern of decrease with increasing stress concentration and was significantly lower at 600 mg Cu·kg^–1 than at 240 mg Cu·kg^–1. In conclusion， this experiment showed that G. orientalis has a measure of tolerance to Cu and Pb stress， and an ability for uptake of these heavy metals.

Effects of altitude and variety on nutrient levels and epiphytes of oats

Gui-qin ZHAO, Ze-liang JU, Ji-kuan CHAI

2022, 31(11):  147-157.  DOI: 10.11686/cyxb2021436

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Oat crops are a major animal feed source in the Qinghai-Tibetan plateau and nearby areas. Typically， the crops are used for making silage rather than hay because of frequent rain at harvest in autumn. However， there is little data on how the yield， forage quality and levels of epiphytes that may affect silage quality of different oat varieties are affected by altitude. Therefore， four oat varieties （Longyan No. 3， Longyan No. 5， Baiyan No. 2 and Bayou No. 3） were planted in 8 localities forming an altitude gradient： Huangzhong （2295 m）， Tianzhu （2797 m）， Shandan （2860 m）， Hezuo （2957 m）， Haiyan （3052 m）， Maqu （3474 m）， Maqin （3765 m） and Chengduo （4217 m）. Measurements included crop yield and dry matter （DM）， water soluble carbohydrate （WSC）， crude protein （CP）， neutral detergent fiber （NDF） and acid detergent fiber （ADF） contents， and counts of lactic acid bacteria （LAB）， molds， yeasts and aerobic bacteria. It was found that there were significant altitude and variety effects on fresh yield， nutritional quality and microbial epiphyte counts. With increase in altitude， fresh yield， WSC， NDF and LAB counts increased （P<0.05）， as much as 284.00%， 15.49%， 10.81% and 11.60% increment were observed at Chengduo site than that at Huangzhong， respectively； meanwhile DM， CP and yeast and mold counts were reduced by 15.67%， 36.27%， 23.53% and 7.75% at Chengduo compared with Huangzhong site， respectively. Among the four tested varieties， Longyan No.5 had the highest fresh yield （75605 kg·ha^-1）， WSC （201.4 g·kg^-1 DM） and NDF （604.2 g·kg^-1 DM） at the Chengduo site， followed by Longyan No.3. The highest CP （119.7 g·kg^-1 DM） and mold counts （4.12 lg cfu·g^-1 FM） were observed in Baiyan No. 2 at the Huangzhong site. Bayou No.3 produced the highest LAB and yeast counts at Maqin and Chengduo sites. In general， Longyan No.3 and Longyan No.5 gave better performance at sites above 3000 m altitude； for sites below 3000 m， the four tested varieties were all found to be suitable for silage production.

Irrigation scheduling based on yield and quality in Bromus inermis

Yuan-bo JIANG, Yan-xia KANG, Guang-ping QI, Min-hua YIN, Yan-lin MA, Jing-hai WANG, Qiong JIA, Yao KANG, Hong-bin ZHANG, Zhong-xia TANG, Ai-xia WANG

2022, 31(11):  158-171.  DOI: 10.11686/cyxb2021350

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A suitably calculated irrigation regime can improve the productivity of artificial grassland， improve the quality of pasture and enhance water use efficiency in drier areas. In this research we compared the effects of two irrigation regimes （regulated deficit irrigation at different growth stages， I₁； regulated deficit irrigation over the whole growth period， I₂） on yield and quality of Bromus inermis in the Hexi Corridor. Irrigation scheduling was optimized by considering the results of field trials and simulations of irrigation scheduling in typical dry years to provide a theoretical basis for local production practices. The results showed that： The yield of B. inermis in I₁ initially increased and then decreased with successive increases in the amount of water applied， while in I₂B. inermis yield showed an increasing trend across the range of irrigation rates tested. In both irrigation regimes， the crude protein content of B. inermis gradually decreased with increasing water supply， while the acid detergent fiber and neutral detergent fiber contents increased somewhat. Compared with I₂， B. inermis yield was increased by 23.11% on average and crude protein content by 6.09% on average in I₁； therefore， the I₁ irrigation regime was superior. Based on the field trial combined with the simulation of irrigation scheduling in a typical dry year， it was found that a treatment designated ［greening stage （75%-85% θ_FC）， jointing stage （65%-85% θ_FC）， and tasseling stage （65%-85% θ_FC） ， I₁DF₁］， irrigation frequency of 12 times， and a total irrigation amount of 521.76 mm provided water-saving benefits and stable yield in B. inermis in the Hexi Corridor.

Relationship between lodging resistance of oats and the basal internode stem characteristics and lignin synthesis

Ming NAN, Jing LI, Gui-qin ZHAO, Ji-kuan CHAI, Yan-ming LIU

2022, 31(11):  172-180.  DOI: 10.11686/cyxb2021416

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Lodging is one of the important factors affecting yield and quality in oat crops. This research studied the physiological mechanisms of lodging resistance in oats， with a view to guiding future breeding. Mengyan 1 and Bayan 6 oat were included in this study as lodging-resistant varieties， while Dingyan 2 and Qingyin 2 were included as lodging-susceptible varieties. Data were collected on the morphological characteristics of basal elongation and differences in the contents of acid detergent fiber， neutral detergent fiber， cellulose and lignin and activities of key enzymes， for these oat cultivars with different lodging susceptibilities， so as to investigate the relationship between the lodging resistance of oats and the morphological characteristics and lignin content and synthase activity in the second-phase elongation at the base of stem. It was found that the amount of lodging among resistant cultivars was lighter and the lodging rate was lower than that of cultivars. The lengths of the second internode at the stem base of lodging easy cultivars were 34.17% higher than those of lodging resistant cultivars. The internode diameter， stem wall thickness， stem weight， density， diameter， force and stem puncture force values of lodging resistant cultivars at the second internode of the stem base were， respectively， 29.11%， 26.18%， 25.80%， 27.97%， 34.61%， 36.23% and 36.60% higher than those of lodging-susceptible cultivars. The stem lignin and cellulose contents of cultivars resistant to lodging were significantly （P<0.05） higher than those of cultivars susceptible to lodging. Lignin content was significantly （P<0.01） positively correlated with the internode breaking force and puncture strength of the second internode at the stem base （r=0.9862 and r=0.9638， respectively）， and significantly negatively correlated with the observed lodging rate （P<0.05， r=-0.9407）. Lignin synthetase tyrosine ammonialyase， phenylalanine aminotransferase， cinnamyl alcohol dehydrogenase and 4-coumaric acid of CoA ligase in stems of lodging-resistant cultivars showed higher activities， resulting in accumulation of lignin at the internodes of the second elongation at the base of stem， which increased the lignification of cell walls and the mechanical strength of stems， and thus enhanced lodging resistance of the oats.

Physiological ecological and secondary metabolic responses of the herbaceous resource plant Thlaspi arvense to salt stress

Na-na LI, Tong-ge LIU, Zhi-hui HUANG, Bao-jiang ZHENG, Yu-hong ZHANG

2022, 31(11):  181-190.  DOI: 10.11686/cyxb2021459

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This research explored the physiological and ecological responses and secondary metabolites of Thlaspi arvense （pennycress） under salt stress in order to develop a theoretical foundation for further research on the planting of salt-tolerant plants on saline-alkali soils. Hydroponically cultured pennycress was grown at 5 NaCl concentrations （0， 50， 100， 150， 200 mmol·L^-1） set to simulate a gradient of salt stress intensity. Leaves of pennycress were collected at 1， 5， 10， and 15 days to determine physiological and biochemical indexes， photosynthetic parameters and secondary metabolite levels. It was found that： 1） The activities of superoxide dismutase， peroxidase， and catalase in the leaves of T. arvense showed a pattern of initial increase and then decrease with increase in salt concentration during the period of salt stress.^{2） The enzyme activity was highest at the NaCl concentration of 100 mmol·L-1. 3） Levels of malondialdehyde first increased and then decreased with increase in salt concentration. 4） The contents of soluble sugar and proline in the leaves of T. arvense increased with increase in salt concentration and with the length of exposure to NaCl stress， while soluble protein levels first increased and then decreased with increase in salt concentration. 5） The chlorophyll a， chlorophyll b， total chlorophyll content， chlorophyll fluorescence parameters， net photosynthetic rate and transpiration rates in T. arvense leaves showed a downward trend with increase in salt concentration， and the decline gradually increased. 6） The contents of total flavonoids， total phenols， and sinigrin in the leaves of T. arvense showed a pattern of initial increase and then decreasing with increase in salt concentration. Thus， pennycress has a high tolerance to salt stress and can maintain normal growth in a salt-stress environment of 50-100 mmol·L-1 NaCl concentration. This result provides a theoretical basis for future research on the salt tolerance mechanisms of T. arvense and other natrophilic plants.}

Progress on the taxonomic classification of Medicago species

Zhi-peng LIU, Guang-peng REN

2022, 31(11):  191-203.  DOI: 10.11686/cyxb2021426

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This review investigates the disordered status of the classificationof Medicago genus， both domestically and internationally. Several definitions of a taxonomic species were considered and the names and characteristics of 13 Medicago species in China are reported， together with a detailed summary of the names， life forms， chromosome numbers， pollination methods and natural distribution of about 90 Medicago species worldwide， including the classification of 14 sections and 10 subsections in Medicago. The molecular evolutionary relationships between different species， and the geographical origin of Medicago are discussed， and the genetic relationships between different subspecies in the alfalfa complex are further explained. This study puts forward a method of identifying Medicago species on the basis of deep understanding of the concept of species. A wide collection of global Medicago germplasm resources， aiming to further clarify the evolutionary relationship among different sections and different species by molecular evolution methods is proposed. This review provides a reference framework for future Medicago classification and alfalfa cross breeding.

Promotional effects of nanoparticles on plants

Yun-hua HAN, Su-juan MI, Xiao-qi SHI, Tian-hang ZHONG

2022, 31(11):  204-213.  DOI: 10.11686/cyxb2021449

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With global climate change and human population increase， the demand for sustainable development of plant production is more urgent. Nanotechnology is one of the most developed sciences in the 21^st century and a promising tool for sustainable agricultural development. In recent years， the applications of nanomaterials for enhancement of plant production have developed rapidly， and potential of this technology in traditional plant production has been proven. In this review， we elucidate the promotional effect of nanomaterials on plant growth and their mechanisms. We discuss developments of nanomaterial research in plant growth， including uptake and transport of nanoparticles， fertilizers and plant growth regulators effects of nano particles， nano enzyme enhancement of stress resistance and nano particle regulation of photosynthesis. Further， the challenges of nanomaterial applications in plant production and research priorities are discussed， emphasizing the need for a systematic approach to the use of nanotechnology in agriculture. We hope this paper will provide new ideas for future research on nanoparticle regulation of plant functions.