Table of Content

20 August 2020, Volume 29 Issue 8

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The relationship between plant functional traits and soil physicochemical properties in alpine meadows in Northwestern Yunnan Province, China

WANG Xiu-yu, HUANG Xiao-xia, HE Ke-jian, SUN Xiao-neng, LÜZENG Zhe-zhou, ZHANG Yong, ZHU Mei, ZENG Rui-qin

2020, 29(8):  6-17.  DOI: 10.11686/cyxb2019473

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The adaptability and distribution of plant species, the process of the construction of plant communities and the function of an ecosystem can be discussed according to the relationship between plant traits and the plant environment. This research sought to link the variation in plant functional traits, the key soil factors that affect plant functional traits and plant functional traits that show a plastic response to soil factors, using data from different categories of alpine meadow in Northwestern Yunnan Province (NYP). Four categories of typical meadow (hydric, mesic, xeric and forest margin meadow) were selected for study, to explore the relationship between plant functional traits and soil properties using RLQ and Fourth-Corner methods. The results showed that: 1) The content of soil total nitrogen increased, while the soil bulk density and C∶N ratio decreased as the soil moisture increased. 2) Most plants were geocryptophytes in alpine meadows and the specific leaf area was negatively correlated with dry matter of the leaf. There were no systematic significant differences in specific leaf area among these four types of alpine meadows. Mesic meadow plants tended to adopt the strategy of single seed breeding, but plants in the other three meadow categories tended to adopt a multiple-seed breeding strategy. 3) The key soil factors that affected community functional traits were soil pH, soil total nitrogen and soil bulk density for the mesic meadow, soil bulk density for the xeric meadow, and soil C∶N ratio for the forest marginal meadow. 4) Key soil factors that affected plant functional traits were soil pH, soil total nitrogen and soil moisture for the mesic meadow, and soil pH, soil total nitrogen, soil bulk density and soil moisture for the xeric meadow. 5) The specific leaf area and life form were the plastic traits of plants which respond sensitively to soil factors in the mesic meadow, while the leaf length∶width ratio, growth form, life form and reproductive strategy were the plastic traits for plants in the xeric meadow.

Effects of nitrogen addition on labile soil organic carbon and carbon pool management index of Stipa baicalensis steppe in Inner Mongolia, China

LIU Hong-mei, ZHANG Hai-fang, ZHAO Jian-ning, WANG Hui, QIN Jie, YANG Dian-lin, ZHANG Nai-qin

2020, 29(8):  18-26.  DOI: 10.11686/cyxb2019477

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The objective of this study was to examine the effects of nitrogen (N) application on labile organic carbon and carbon pool management index of the Stipa baicalensis steppe in Inner Mongolia, China. The treatments in the manipulative experiment included N additions at rates of 0 (control), 50, 100, 200 and 300 kg N·ha^-1·yr^-1 (designated N₀, N₅₀, N₁₀₀, N₂₀₀ and N₃₀₀, respectively). It was found that, compared to N₀, the N₅₀, N₁₀₀, N₂₀₀ and N₃₀₀ treatments significantly increased the contents of readily oxidized soil organic carbon and dissolved organic carbon, while decreasing the content of microbial biomass carbon. The N₁₀₀ treatment significantly increased the proportion of readily oxidized organic carbon and the proportion of dissolved organic carbon, and significantly increased the soil carbon activity, carbon pool activity index and carbon pool management index. The N₂₀₀ and N₃₀₀ treatments significantly decreased the proportion of readily oxidized organic carbon, and significantly decreased the soil carbon activity, carbon pool activity index and carbon pool management index. A correlation analysis indicated that there was a significant positive correlation between the proportion of readily oxidized organic carbon, the proportion of dissolved organic carbon, the proportion of microbial biomass carbon, the carbon pool index and the carbon pool management index. Chronic increase in N deposition may reduce the quality of the carbon pool in the S. baicalensis steppe.

Effect of carpet mesh implantation on hybrid turf stability and performance quality

ZHANG Tong-rui, LI Fu-cui, LI Hui, JI Shuang-xuan, FAN Zhi-hao, CHEN Yu-feng, CHAO Yue-hui, HAN Lie-bao

2020, 29(8):  27-36.  DOI: 10.11686/cyxb2020054

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This research studied the effect of carpet mesh implantation on carpet mesh hybrid turf performance and soil-bed stability. The grass species used was perennial ryegrass (Lolium perenne cv. Neruda 1BT). Treatments comprised a control with no carpet mesh and comparison of three carpet mesh types (A, 15 mm×15 mm mesh with no backing; B, 30×30 mm mesh with backing; C, 20 mm×12.5 mm mesh with backing) implanted below the soil surface, in foam boxes 35 cm×23 cm in area and 19 cm deep, and filled with pure sand predominantly 0.1-0.5 mm particle size. Measurements included aboveground and underground biomass, root morphological parameters (root length, root surface area, root volume and root vigour), and testing of the soil-bed stability of the hybrid turf using a direct shear test. It was found that carpet implantation significantly decreased turfgrass performance, with decline in color, NDVI and density. The density decline with implantation of the three carpet types at day 116 from planting was 20.8%, 8.7% and 14.7% at the 116th day, for carpet mesh types A, B and C, respectively. However, carpet types with mat(B and C) increased the turfgrass uniformity. Furthermore, compared with the control, carpet implantation decreased the underground biomass, root length, root surface area and root volume, and also compromised root vigour, both above and beneath the carpet. Carpet implantation did increase the turf shear strength (by 51.9%, 162.7% and 134.6%, for mesh types A, B, and C, respectively), surface firmness (by 34.6%, 32.8% and 45.8%, for mesh types A, B, and C, respectively), and increased cohesion compared to the control. In summary, in the artificial-natural hybrid turf, the carpet implantation inhibited the growth of roots, which compromised the aboveground growth of the turf grass and turf performance. Carpet implantation, especially carpet with mat, did increase the mechanical stability of the hybrid turf.

Effects of nitrogen and phosphorus addition on C∶N∶P ecological stoichiometry in leaves and roots of different canopy species in Hulunbuir grassland

WANG Hong-yi, DING Rui, WANG Zhi-hui, YANG Feng-jun

2020, 29(8):  37-45.  DOI: 10.11686/cyxb2020093

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Carbon (C), nitrogen (N), and phosphorus (P) ecological stoichiometry can indicate the interactions between plants and environment, which is an important basis for evaluating the response of plants to environmental changes. At present, most of the studies of ecological stoichiometry are about plants and leaves, the aboveground parts of plants, and few studies have investigated roots. Here we report a three-year nitrogen and phosphorus addition experiment with two nitrogen rates (0, 10 g N·m^-2·yr^-1) two phosphorus rates (0, 10 g P·m^-2·yr^-1), and the interaction between the two (N₀P₀ control, and N+P), a total of four treatments, with each treatment repeated five times. Two canopy upper-layer species (Leymus chinensis and Thermopsis lanceolata) and two understory species (Potentilla acaulis and Cymbaria dahurica) in Hulunbuir grassland were investigated, and the effects of nitrogen and phosphorus addition on C∶N∶P ecological stoichiometric characteristics in leaves and roots were analyzed. It was found that nitrogen and phosphorus addition had no impact on C contents in leaves and roots of the four species. Nitrogen addition significantly increased N contents and decreased C∶N in leaves and roots of the three non-leguminous plants, though the effect on P. acaulis leaves was marginal. Phosphorus addition significantly increased P contents and decreased C∶P in leaves and roots of the four species. Nitrogen and phosphorus addition had no significant interaction effects on C, N, or P contents or stoichiometric ratio. C∶N, and C∶P of L. chinensis was the highest among the four species, and thus, we inferred that higher nutrient utilization efficiency was one of key factors for L. chinensis to become a dominant species and a constructive species. In addition, N was the main limiting factor, judging by the N∶P ratio in plant leaves. Therefore N∶P of leaves and not N∶P of roots should be used as the criterion when determining nutrient limitation. Overall, our study suggested that the above and below-ground organs had a synergistic response to nitrogen and phosphorus addition, and the canopy height of plants had no significant effect on C, N, and P ecological stoichiometric characteristics.

Effects of AMF on growth and photosynthetic physiological characteristics of Leymus chinensis and Medicago sativa with and without nitrogen and phosphorus application

SHAN Li-wen, ZHANG Qiang, ZHU Rui-feng, KONG Xiao-lei, CHEN Ji-shan

2020, 29(8):  46-57.  DOI: 10.11686/cyxb2019459

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Symbiosis between arbuscular mycorrhizal fungi (AMF) and forage plants plays an important role in the utilization efficiency of plant nutrients in grassland. Mixed sowing of legumes and grasses can effectively increase grassland yield through biological N fixation, and the addition of appropriate amounts of external nitrogen and phosphorus can also further promote herbage growth. In order to better manage the utilization efficiency of grassland in the future, the optimal combination of plant species, AMF and nitrogen and phosphorus will need to be known. Therefore, an experiment was conducted with the presence or absence of arbuscular mycorrhizal fungi (+/- AMF) as the main treatment, and different nitrogen and phosphorus fertilizer additions (N₀, no added N or P; N₁, 2.0 g N and 0.2 g P·m^-2; N₂, 20.0 g N and 2.0 g P·m^-2) as secondary treatments, to study the plant growth and photosynthesis response of coexisting alfalfa communities. It was found that: 1) AMF significantly improved the net photosynthetic rate of Leymus chinensis and Medicago sativa. 2) The light response curve indicated that the net photosynthetic rate of L. chinensis and M. sativa increased with increase in light intensity, and the net photosynthetic rate of +AMF L. chinensis was higher than -AMF L. chinensis. 3) AMF significantly increased the chlorophyll content of L. chinensis and M. sativa. Under different nitrogen and phosphorus application rates, the chlorophyll content of +AMF L. chinensis and M. sativa +AMF was higher than that of the -AMF treatments. 4) The application rate of nitrogen and phosphorus and the AMF treatment significantly affected the biomass of L. chinensis and M. sativa. In this research, treatment that optimized herbage production of coexisting communities of alfalfa-grass mixed grassland was +AMF+N₂.

Effects of different phosphorus supply levels on morphology and physiology of Paspalum wettsteinii

SUN Xiao-fu, HUANG Li-juan, WANG Pu-chang, ZHAO Li-li, LIU Fang

2020, 29(8):  58-69.  DOI: 10.11686/cyxb2019471

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This research explored the morphological and physiological changes of Paspalum wettsteinii under different phosphorus supply levels, to understand the adaptation strategies to low phosphorus stress, and to provide a theoretical foundation for understanding phosphorus nutrient management and physiological regulation in P. wettsteinii. The experiment was carried out using a sand culture method, and treatments comprised 5 levels of phosphorus: 2, 20, 200, 600 and 1000 μmol·L^-1, with 200 μmol·L^-1 regarded as the control. The changes in seedling growth, root morphology and protective enzyme activity were measured at 10, 20 and 30 days after the imposition of stress. It was found that under low phosphorus supply, the height and aboveground biomass were significantly decreased (P<0.05), with leaf area and leaf perimeter also showing a decreasing trend. Meanwhile, the root biomass, total root length, root surface area, root volume, number of root tips and root∶shoot ratio were all higher at the low phosphorus supply than in the control. Superoxide dismutase, peroxidase (POD), catalase (CAT) and acid phosphatase (ACP) activities were significantly enhanced (P<0.05), and leaf lamina and root conductivity were significantly improved (P<0.05) under low phosphorus supply levels. Principal component analysis showed that CAT activity, POD activity, root acid phosphatase activity, number of root tips and root membrane permeability were significantly affected by phosphorus stress, and better performance when the phosphorus supply level is 600 μmol·L^-1 than others. At the phosphorus supply level of 200 μmol·L^-1, the multi-trait performance of P. wettsteinii was ranked second, and was exceeded only at the high phosphorus level. Partial least squares regression analysis was used to analyze the relationship between each index parameter and plant biomass under different phosphorus supply levels of P. wettsteinii, and it was concluded that root surface area, root acid phosphatase activity (ACP) and leaf perimeter were crucial indexes affecting the biomass of P. wettsteinii. In summary, these results show that P. wettsteinii adapted to low-phosphorus stress through reducing above-ground biomass, increasing root weight and root surface area, and promoting protective enzyme activity.

Yield effect of optimisation of photosynthetic characteristics of alfalfa through balanced fertilization

TONG Chang-chun, LIU Xiao-jing, LIN Fang, YU Tie-feng

2020, 29(8):  70-80.  DOI: 10.11686/cyxb2019467

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This research explored the effects of balanced fertilization on photosynthetic characteristics and yield of alfalfa, in order to clarify the contribution of photosynthetic performance to herbage accumulation in alfalfa, in a field experiment. The alfalfa variety ‘Gannong No.3’ alfalfa was used as plant material and the ‘3414’ experimental design, an incomplete factorial of N, P and K fertilizer applications widely used in China over the last 15 years, was adopted in this study. It was found that: 1) Balanced fertilization enhanced the photosynthetic characteristics of alfalfa by increasing chlorophyll content, RuBP carboxylase activity, photosynthetic rate, carbohydrate content and population leaf area index. The combined application of N at 103.5 kg·ha^-1, P₂O₅ at 105 kg·ha^-1 and K₂O at 90 kg·ha^-1 was the combination that optimized the photosynthetic characteristics of alfalfa. This nutrient combination can therefore be described as balanced fertilization. 2) Under balanced fertilization, the hay yield of alfalfa was significantly increased, and the total annual yield reached 25636.26 kg·ha^-1. Compared with other fertilizer combinations tested, balanced fertilization ensured efficient alfalfa production. 3) Through the principal component analysis of normalized data, it was found that the population leaf area index, RuBP carboxylase activity and chlorophyll were the photosynthetic factors that contributed the most to the yield development of alfalfa. The influence on yield of these factors was, respectively, 22.8%, 21.3% and 15.9%. To summarize, balanced fertilization is an important to obtaining a high yield when growing alfalfa, and the production performance of alfalfa can be effectively improved by regulating the main photosynthetic factors such as leaf area index, RuBP carboxylase activity and chlorophyll content.

Effects of fertilization on growth and yield of continuously cropped sweet sorghum

Zaituniguli Kuerban, Tuerxun Tuerhong, TU Zhen-dong, WANG Hui, Shan Qimike, Aikebaier Yilahong

2020, 29(8):  81-92.  DOI: 10.11686/cyxb2019398

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This research explored the effect of a range of different fertilizer regimes on crop performance of the sweet sorghum variety ‘Xin Gaoliang No.3’ under long-term continuous cropping in the arid region of Xinjiang Province. The experiment comprised eight fertilizer treatments designated CK (control), NK, NP, PK, NPK, M (organic manure fertilizer), NPKM and 1.5NPKM. The traits monitored for ‘Xin Gaoliang No.3’ included plant height, stem diameter, leaf number, brix sugar level, chlorophyll content and yield, among others. The different fertilizer treatments significantly affected a majority of agronomic traits. In general, trends in the different measures (plant height, stem diameter, leaf number, sugar brix content and chlorophyll content) were basically the same for any given fertilizer treatment as the crop developed, but there were differences between the different treatments. At crop maturity, the plant height, stem diameter and brix sugar content were 224.33 cm, 21.47 mm and 18.41%, respectively, for the NPKM fertilizer treatment and these values were significantly higher than those of all other treatments and, respectively, 13.86%, 39.60% and 23.47% greater than in the CK treatment. Fertilization enhanced brix sugar levels in the stem. The stem brix sugar value peaked (18.57%) on the 28th day after mean heading date. but the accumulation patterns brix sugar at different stem nodes from the heading to the maturity differed between fertilization treatments. The pattern of change in chlorophyll content with crop development was basically a constant gradual increase, which peaked at 44.62 SPAD units for the NPKM treatment. The straw yield, grain yield and biomass yield for all fertilizer treatments were significantly higher than those for CK. The straw yield, grain yield and biomass values for the NPKM treatment were 90.80, 4.01 and 94.81 t·ha^-1, respectively, and were the highest among all the treatments. Fertilizer application is beneficial to increase the yield, brix sugar and economic benefit of sweet sorghum. To improve the sustainability of a continuous sweet sorghum cropping system, the choice of fertilizer should be considered. In general, mixed application of organic and inorganic fertilizers (NPKM) is the best fertilizer regime to enhance sustainability of continuous sweet sorghum cropping system in the arid regions of Xinjiang Province.

Effect of green manure retention practices on nitrogen absorption and utilization by maize crops in the arid oasis irrigation area

LÜ Han-qiang, YU Ai-zhong, WANG Yu-long, SU Xiang-xiang, LÜ Yi-tong, CHAI Qiang

2020, 29(8):  93-103.  DOI: 10.11686/cyxb2020020

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Nowadays, the major issues facing crop husbandry in the arid oasis irrigation region are the sustainability of long-term continuous cropping of wheat and maize, the long period of fallow after the wheat harvest, and a comparatively low nitrogen (N) fertilizer use efficiency. Therefore, investigation of the effects of different green manure retention practices on nitrogen absorption and utilization of subsequent maize crops is of significant importance, and a field experiment was conducted in the Shiyang river basin to determine the effects of different green manure retention practices on nitrogen use characteristics of subsequent maize crops in a wheat-green manure-maize rotation system. Green manure retention practices evaluated were: i) Tillage with the total green manure crop incorporated into the soil, ii) No-tillage with the total green manure crop mulched on the soil surface, iii) Tillage with green manure crop roots incorporated in the soil and with above ground herbage removed; iv) No-tillage with above ground green manure crop herbage removed, and vi) Conventional tillage without green manure. It was found that before maize sowing, the treatments with the total green manure crop incorporated into the soil or mulched on the soil surface increased the soil mineral nitrogen content by 11.7% and 10.0%, respectively, and improved the microbial biomass nitrogen content by 14.3% and 16.2%, respectively, compared with conventional tillage without green manure. At the tasseling and silking stages, the two treatments increased soil mineral nitrogen content by 17.0% and 13.7%, respectively, and improved microbial biomass nitrogen content by 8.7% and 10.7%, respectively, in the 0-30 cm soil layer, which allowed efficient use of nitrogen by the maize. These two treatments also significantly increased above-ground nitrogen accumulation both in leaves and stems, and in the grain. As a result, the N use efficiency of these two treatments increased by 20.1% and 25.8%, respectively, and the N partial productivity by 17.3% and 22.2%, respectively, compared to conventional tillage without green manure. Furthermore, the N fertilizer use efficiency and nitrogen use efficiency of the two treatments were significantly higher than those for the treatment with green manure roots retuned only. In summary, in the arid oasis irrigation area, the practices of incorporating the total green manure crop into the soil or mulching the total crop on the soil surface using no-tillage, can increase soil nitrogen content while at the same time facilitating increased nitrogen use efficiency in maize.

Effects of light quality on growth, and physiological and biochemical traits of Sarcandra glaba seedlings

XIE De-jin, LI Jing-wen, YE You-jie, YIN Biao, REN Ke, CHEN Ling-yan, RONG Jun-dong, ZHENG Yu-shan

2020, 29(8):  104-115.  DOI: 10.11686/cyxb2019465

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This research aimed to explore in detail the effects of three light regimes [white light (WL), red light (RL), and blue light (BL)] on growth status and physiological and biochemical traits of Sarcandra glaba seedlings. Measures of plant growth status conducted were: plant height, stem diameter, total fresh weight (roots and shoots), total dry weight (roots and shoots), root morphology indexes, and root∶shoot ratio. Physiological and biochemical traits measured included chlorophyll, solution protein, solution sugar, reducing sugar, and malondialdehyde (MDA) concentrations of leaf tissues; peroxidase (POD) and superoxide dismutase (SOD) activities, net photosynthetic rate (P_n), maximum light use efficiency (LUE_max), maximum water use efficiency (WUE_max) and maximum photosynthetic efficiency (F_v/F_m). Most of the measured traits showed differences between light regimes. Compared with WL and BL groups, the RL treatment resulted in a significant reduction in a majority of the measured traits. Exceptions were plant height and WUE_max which were increased in RL. Compared with the WL treatment, in the BL light regime, root morphology indexes, root∶shoot ratio, protein and MDA concentrations, POD and SOD activities and WUE_max were considerably increased, while other indexes were decreased. In this experiment, the RL treatment resulted in a significant decrease in many traits. Meanwhile, the BL regime not only stimulated root morphology indexes, but also improved WUE_max. This research lays a theoretical foundation for developing light quality guidelines for the cultivation of S. glaba seedlings.

Changes in photoinhibition and fatty acid composition in the thylakoid membrane of kidney bean leaves under low temperature and weak light stress

WANG Yu-ping, GAO Chun-xiao, WANG Sheng-xiang, HE Xiao-tong

2020, 29(8):  116-125.  DOI: 10.11686/cyxb2020072

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This research investigated the changes in photoinhibition and fatty acid composition in thylakoid membrane under combined stresses of low temperature and weak light in two varieties of kidney bean, ‘British big red’ and ‘Shanxi small red’, which have different sensitivity to low temperature and weak light. The main lipids in the thylakoid membrane are monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG), phosphatidylcholine, phosphatidylglycerol (PG) and sulphoquinovosyl diglyceride (SQDG). The fatty acid composition of the thylakoid membrane, together with photosynthetic and chlorophyll (Chl) fluorescence parameters were determined during stress and recovery. It was found that with increase in stress duration, the content of Chl a, Chl b and Chl (a+b) decreased while the ratio of Chl a/b increased. Compared to the control, the maximum quantum yield of PSⅡ (F_v/F_m), the efficiency of excitation capture by open PSⅡ reaction centers (F_v'/F_m'), the photochemical quenching coefficient (qP) and the actual PSⅡ efficiency (Φ_PSⅡ) declined, but Chl a/b and the non-photochemical quenching (NPQ) increased. With more prolonged stress duration MGDG, DGDG and SQDG, and thylakoid membrane content of linolenic acid (C18:3) were substantially reduced and the content of palmitic acid (C16:0) was concomitantly increased. These changes with increased stress duration represented an increased content of saturated fatty acids, and a decreased content of unsaturated fatty acids (UFA), polyunsaturated fatty acids (PUFA) and degree of membrane unsaturation in the thylakoid membrane lipids. However, there were also changes in the PG fraction which contributed to maintaining the overall degree of unsaturation in membrane lipids. This pattern was reversed during the recovery period. The correlation coefficients between PUFA and F_v/F_m of ‘British big red’ and ‘Shanxi small red’ kidney beans were 0.8621 and 0.8392, respectively. Compared to ‘British big red’ kidney beans, stress caused more serious photoinhibition in PSⅡ of ‘Shanxi small red’ kidney bean leaves. Therefore, it can be postulated from these results that the reason for the increased the stability of the thylakoid membrane and reduced photoinhibition of PSⅡ in ‘British big red’ kidney beans may be the higher membrane content of UFA, especially PUFA.

Effects of water stress on yield, quality and trace element composition of alfalfa

LU Jiao-yun, XIONG Jun-bo, ZHANG He-shan, TIAN Hong, YANG Hui-min, LIU Yang

2020, 29(8):  126-133.  DOI: 10.11686/cyxb2019462

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Drought seriously affects the growth and production of forage crops and has long been one of the most important limiting factors for animal husbandry in the Loess Plateau of China. Understanding of forage response to water deficit can help to optimize grassland management and improve productivity. This study was carried out in a greenhouse with alfalfa (Medicago sativa) under four water levels of 35%, 50%, 65% and 80% field saturated water capacity (FWC) to clarify the influence of water deficit on forage yield and quality. It was found that: 1) With increasing water stress, the height and fresh and dry weight per plant of alfalfa decreased significantly (P<0.05), although fresh and dry weight per plant did not differ between 65% FWC and 80% FWC. 2) The neutral detergent fiber content (NDF) of alfalfa at 50% FWC was significantly lower than that under 65% FWC (P<0.05), but did not differ from NDF at other water levels. The crude protein content at 35% FWC and 80% FWC were significantly higher than those at 50% FWC and 65% FWC. There was no significant difference in digestible dry matter, total digestible nutrient, digestible dry matter intake and relative feeding value among various levels of water deficit. 3) Copper and Fe concentrations initially increased and then decreased with increasing water stress, while Mg and Mn concentrations showed an opposite trend and Zn concentration increased. The accumulations of five trace elements tested differed little among the different levels of water stress, except that Mg and Mn accumulations were significantly higher at 80% FWC than at 35% FWC and 50% FWC. In summary, mild water stress was conducive to the improved yield and quality. At 50% FWC, alfalfa forage showed lower fiber content and higher nutritional value, while at 65% FWC, alfalfa showed higher yield. Trace elements Mn, Mg, Cu and Fe can reflect the quality characteristics of alfalfa to a certain extent.

Effects of acid stress on chlorophyll fluorescence characteristics and root antioxidant activity of Prunella vulgaris

ZHANG Li-xia, CHANG Qing-shan, XUE Xian, LIU Wei, ZHANG Qiao-ming, CHEN Su-dan, ZHENG Yi-qi, LI Jing-lin, CHEN Wan-dong, LI Da-zhao

2020, 29(8):  134-142.  DOI: 10.11686/cyxb2019466

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This research aimed to elucidate the tolerance of Prunella vulgaris seedlings to acid environments. Hoagland nutrient solutions with a range of pH values (pH=4.5, 4.0, 3.5, 3.0) were used to simulate environmental acid stress, and the effects of acid stress on chlorophyll fluorescence characteristics and root antioxidant activity were studied. It was found that at lower pH the quantum efficiency of PSⅡ electron transfer (φE_o) in leaves of P. vulgaris decreased, while a number of other fluorescence parameters increased, including: the variable fluorescence F_k to the amplitude F_j-F_o (W_K), relative variable fluorescence at J step (V_J), QA- maximum rate of reduction (dV/dt_o). The absorption flux per reaction center (ABS/RC), trapped energy flux per RC (TR_o/RC) and dissipated energy flux per RC (DI_o/RC) increased, but electron transport flux per RC (ET_o/RC) decreased gradually. The maximum quantum yield of PSⅡ (F_v/F_m), the photosynthetic index based on absorption basis (PI_abs), the maximum PSⅠ redox activity (ΔI/I_o), and the coordination of photosystem between Ⅰ and Ⅱ (Φ_PSⅠ/PSⅡ) all decreased under acid stress. The activity of superoxide dismutase (SOD) and peroxidase (POD) in roots decreased, but the activity of ascorbic acid peroxidase (APX) in roots increased on initial exposure to acid stress and then decreased. The soluble sugar and proline concentrations in leaves of P. vulgaris increased with the decrease in pH value. In summary, the PSⅡ reaction center of P. vulgaris was damaged, the electron transfer was blocked, the photosystem performance and the coordination of photosystem between Ⅰ and Ⅱ were reduced under acid stress, and the activities of SOD and POD in roots were inhibited, the latter being most obvious in the pH 3.0 treatment. P. vulgaris was able to reduce the damage to the photosynthetic mechanism by increasing the heat dissipation capacity of unit reaction center, and reduce the damage caused by acid stress by increasing the APX activity in roots and the concentration of osmolytes in leaves.

A multi-trait evaluation of salt tolerance of 5 oat germplasm lines at the seedling stage

WANG Miao-miao, ZHOU Xiang-rui, LIANG Guo-ling, ZHAO Gui-qin, JIAO Run-an, CHAI Ji-kuan, GAO Xue-mei, LI Juan-ning

2020, 29(8):  143-154.  DOI: 10.11686/cyxb2019492

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In order to determine the salt tolerance of different oat breeding materials at the seedling stage and select elite oat germplasm lines, five screened salt-tolerant oat germplasm lines from a previous experiment (Baiyan No.7, Longyan No.4 and No.5, and Qingyongjiu 30 and 195), were studied in this research. In a sand culture experiment, 3-week old seedlings were treated with 0.9% NaCl solution for 7 days, and the growth characteristics, photosynthetic characteristics, chlorophyll fluorescence parameters, antioxidant enzyme activities, tissue malondialdehyde (MDA) concentration, and osmolyte content were measured. The salt tolerance of the five oat germplasm lines was evaluated by principal component analysis and membership function analysis of the seedling data. It was found that there were significant differences (P<0.05) between the tested germplasm lines for performance under salt stress. Qingyongjiu 195 had a larger root surface area and root volume, a higher K⁺ content, a lower MDA content, and higher net photosynthetic rate, electron transfer rate, photochemical quenching, chlorophyll content and peroxidase activity, than the other 4 tested varieties. Meanwhile, Qingyongjiu 30 had greater superoxide dismutase and catalase activities than other germplasm lines. Through principal component analysis, inorganic osmotic regulation substances, membrane lipid peroxidation and antioxidant enzyme activity were identified as traits which could be used in a multi-trait evaluation index for salt tolerance of oats at the seedling stage. According to the multi-trait index of salt tolerance (D), the salt tolerance of the germplasm lines ranked as follows: Qingyongjiu 195>Baiyan No.7>Qingyongjiu 30>Longyan No.5>Longyan No.4.

A multi-trait evaluation of drought resistance of bermudagrass (Cynodon dactylon) germplasm from different habitats in Xinjiang province

ZENG Ling-shuang, LI Pei-ying, SUN Xiao-fan, SUN Zong-jiu

2020, 29(8):  155-169.  DOI: 10.11686/cyxb2019486

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This research used two commercial varieties of bermudagrass (Cynodon dactylon) as control and evaluated performance of 41 germplasm accessions of bermudagrass collected from different habitats in Xinjiang province under drought and control treatments. After 30 days of drought treatment, the chlorophyll content, green leaf proportion, relative conductivity, leaf relative water content, proline content, malondialdehyde content, speed of growth and aboveground biomass under natural drought stress were measured. Based on these data, correlation analysis and principal component analysis were performed to construct multi-trait evaluation indicators, and combined with membership function analysis, cluster analysis, grey correlation analysis and discriminant analysis methods to comprehensively evaluate multiple trait expression linked to drought resistance, develop key indexes for identification of drought resistance, and clarify the relationship between drought resistance of germplasm accessions and their habitat climate zone. It was found that the relative conductivity, proline and malondialdehyde content of the tested germplasm significantly increased under drought stress, and the relative water content, chlorophyll content, aboveground biomass, speed of growth and green leaf rate significantly decreased. There were differences in response to drought stress between all indices. The eight measured traits were reduced by principal component analysis to six independent scores, representing 87.34% of the total data variation. The result of membership function analysis based on drought resistance comprehensive evaluation value (D), comprehensive drought resistance coefficient (CDC), and weighted drought resistance coefficient (WDC) analysis and cluster analysis showed that accessions designated C₁₁₈, C₁₃₈ and C₂₄ had strong drought resistance, while accessions designated C₁₀, C₁₃₄ and C₃₂ had weaker drought resistance. The grey correlation analysis indicated that relative conductivity, leaf chlorophyll content and malondialdehyde content could be used as key indexes for drought resistance evaluation of bermudagrass germplasm, and discriminant analysis indicated that there was no significant correlation between drought resistance of Xinjiang Bermudagrass germplasm and its habitat climate zone. The comprehensive analysis showed that the drought resistance of C₁₁₈, C₁₃₈, C₂₄ and other germplasm acessions was better than that of the commercial variety Tifway. Hence this research has provided excellent germplasm for breeding new bermudagrass varieties with good drought resistance, and provided materials for further study of physiological and molecular mechanisms of bermudagrass drought resistance.

Cloning and expression analysis of TrSAMDC1 in white clover

HOU Jie-ru, DUAN Xiao-yue, LI Zhou, PENG Yan

2020, 29(8):  170-178.  DOI: 10.11686/cyxb2019475

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S-adenosyl-L-methionine decarboxylase (SAMDC) plays an important role in plant abiotic stress resistance. In this study, a 1559 bp full-length SAMDC gene of white clover (Trifolium repens) were cloned by molecular biology technology and named TrSAMDC1. Bioinformatics analysis indicated that TrSAMDC1 has an open reading frame of 1077 bp. The TrSAMDC1 gene encodes an unstable hydrophilic protein of 358 amino acids without transmembrane structure and acting as a signal peptide, which might be located in the cytoplasm. The main components of the secondary structure were a random coil, and the tertiary structure was a homologous dimer. The phylogenetic tree indicates that TrSAMDC1 was closely related to SAMDC of other Leguminosae and highly conserved in evolution. The expression patterns of TrSAMDC1 demonstrates tissue, organ and spatio-temporal specificity under abiotic stress including heavy metal cadmium (CdSO₄), low temperature (4 ℃), high temperature (35 ℃), drought (PEG-6000) and salt (NaCl) and hormone treatments [such as 100 μmol·L^-1 abscisic acid (ABA) and 1 mmol·L^-1 auxin (IAA)]. All treatments could significantly up-regulate the relative expression of leaves TrSAMDC1, and reached the peak after 12 h in most treatments. Although the roots expression of TrSAMDC1 was different from that of control, the sensitivity of roots was significantly lower than that of leaves. The results showed that the TrSAMDC1 could regulated growth and development and responses abiotic stress, especially to high temperature and heavy metal cadmium stress.

Effect of propionic acid on the storage stability of high moisture purple prairie clover (Dalea purpurea) hay

PENG Kai, WANG Guo-xia, HUANG Yan-hua, WANG Yu-xi

2020, 29(8):  179-187.  DOI: 10.11686/cyxb2020078

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Purple prairie clover (PPC; Dalea purpurea) is an important legume that grows naturally on rangeland and has a feeding value similar to alfalfa. Baling hay with high moisture content is beneficial to shorten the field drying period and thereby reduce the risks of losses, but high-moisture hay is difficult to store as the high moisture content may result in degradation, loss of nutritive value, and sometimes toxic fungal growth in the stack. The effect of propionic acid on the stability of PPC hay bales with high moisture content was studied. The results indicated that PPC hay baled at high moisture content (28%) had similar chemical composition to those baled at low moisture content (17%). However, PPC hay baled at high moisture content was perishable and not easily stored. Inclusion of buffered propionic acid with at an appropriate rate in PPC hay bales baled at high moisture content was observed to significantly reduce the temperature in storage and forage pH, the neutral and acid detergent fibre levels, and numbers of bacteria, fungi and yeasts, especially after longer periods of storage (P<0.05), while at the same time increasing the crude protein and water soluble carbohydrate content of bales during storage. In summary, adding propionic acid to high moisture PPC hay bales, enhances their nutritional value, feeding safety and storage stability.

Effect of meteorological factors on the population of plateau zokor

GUO Qiang, WANG Yu-qin, BAO Gen-sheng, WANG Hong-sheng

2020, 29(8):  188-194.  DOI: 10.11686/cyxb2019474

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The plateau zokor (Myospalax baileyi) is one of the main rodent species in the Qinghai-Tibet Plateau. Understanding the impact of meteorological factors on the growth and decline of the plateau zokor population is of high relevance to managing the maintenance of biodiversity. The population density of the plateau zokor was studied from 2013 to 2016. Pearson correlation analysis and canonical correspondence analysis (CCA) were used to study the population density of the plateau zokor and the correlation between the grassland biomass and seven meteorological factors in the disturbance zone. It was found that the population density and grassland biomass of the plateau zokor showed a downward trend over the study period, and the density of plateau zokor was significantly positively correlated with the biomass of dicotyledons (P<0.05). The temperature and precipitation strongly influenced the population and biomass of the plateau zokor. The annual mean temperature and the annual mean minimum temperature were significantly correlated with the population density of the plateau zokor (P<0.05). In addition, the population density of the plateau zokor and sunshine hours are closely related. Meteorological factors have an indirect effect on the food supply of plateau zokor.

Knowledge mapping analysis of grassland carbon sink research based on CiteSpace

GAO Yu-juan, SHI Jiao, LI Xin

2020, 29(8):  195-203.  DOI: 10.11686/cyxb2019490

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This study surveyed the literature on grassland carbon sink in core journals accessed through Web of Science from 2010 to 2019 using CiteSpace software to identify any apparent trends and to identify the sphere of influence of existing research of different countries, institutions, journals and individuals. It was found that with respect to global grassland carbon sink, China ranks first, followed by the United States and Germany. In terms of international cooperation, the UK contributes the most, and other countries need to strengthen cooperation and share results. The institution with the largest number of papers is the Chinese Academy of Sciences, far exceeding other institutions. The journal ‘Global Change Biology’ is a clear leader in the number of citations and has a great influence in academia. German scholar Klaus Butterbach-Bahl is the most prolific author and has made a great contribution to the field, but the cooperation between other authors needs to be strengthened. An analysis of hot topics and research frontiers indicates a need to strengthen the effort invested in comprehensive assessment of grassland carbon balance, enhance the sophistication of research methods, and expand research volume.