Table of Content

20 September 2020, Volume 29 Issue 9

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Memorial to Murray Hill, a New Zealand professor in seed science

NAN Zhi-biao, WANG yan-rong

2020, 29(9):  1-4.  DOI: 10.11686/cyxb20200901

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Energy balance analysis of farm production systems in the transitional zone between the Loess Plateau and the Qinghai Tibet Plateau, China——A case study of the Tongwei-Weiyuan-Xiahe transect

CONG Yi-ming, GAO Xiao-ye, HOU Fu-jiang

2020, 29(9):  5-19.  DOI: 10.11686/cyxb2019532

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The transitional zone between the Loess Plateau and the Qinghai-Tibet Plateau (LP-QTP) has become recognized as a region with one of the most sensitive and fragile environments in China from an ecological perspective, with high susceptibility to climate change. Agriculture is important in the region and energy supply is the driving force for sustainable development of farm structure and function in agricultural production systems, and is an important indicator for measuring the ecological and production benefits of agricultural production systems. In this paper, a Tongwei (TW)-Weiyuan (WY)-Xiahe (XH) transect was established in the LP-QTP transitional zone to analyze the energy output of agricultural production systems on the altitude gradient (approx. 2000-3000 m above sea level). The results showed that: 1) In crop production systems the energy input, energy output, energy income and energy efficiency decreased from the LP to the QTP. When the farmers percentage accounted for 50% (as identified by logistic regression), energy income of farms in TW and WY were 104.80 and 44.59 GJ, respectively. 2) In livestock production systems, the energy input per household was the highest in WY and lowest in XH. Energy income of XH, TW and WY were 160.42, -47.43 and -55.25 GJ, respectively. The energy output, energy income and energy efficiency all progressively increased with the altitude. 3) In crop-livestock integrated systems energy input ranked WY>TW>XH, while energy output, energy income and energy efficiency ranked XH>TW>WY. The threshold of energy income of XH, TW and WY were 91.54, 16.50 and 76.98 GJ, respectively, when the farmers percentage accounted for 50%. The point is most sensitive to energy changes, and regulating energy behavior can maximize the benefits. 4) The Shannon-wiener diversity index, Pielou evenness index and energy efficiency of the agricultural production systems were significantly correlated (P<0.05). The structural equation model indicated that altitude was the most significant factor determining energy balance of crop-livestock production systems (P<0.05). The results provide a scientific basis for agricultural production development and policy formulation in the transition zone, based on system energy balance.

Research on sustainable development of Maqu County over the past decade based on ecological footprint

TENG Rui, LI Guang, LUO Yong-zhong, YU Wen-hui, MA Wei-wei, CHEN Guo-peng, LIU Qiang, WANG Jun, ZHUO Ma-cao, YUAN Jian-yu, ZHANG Shang-wen

2020, 29(9):  20-27.  DOI: 10.11686/cyxb2019506

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Maqu County is an important indicator region for the stability and maintenance of the Qinghai-Tibet Plateau and includes the upper reaches of the Yellow River. It is of great significance to study the sustainability of its ecological environment and social and economic development. The ecological footprint model was applied to study the changes in per capita ecological footprint, ecological carrying capacity, ecological deficit and sustainable development index of Maqu County from 2007 to 2016. The results indicate that the per capita ecological footprint of the study area increased significantly in the past 10 years, from 4.26 ha in 2007 to 5.91 ha in 2016, an increase of 38.73%. Pasture accounted for 98.83% of the per capita ecological footprint of the region, ecological carrying capacity trended downward from 3.74 ha in 2007 to 3.04 ha in 2016, with a drop of 18.72%. In this region, all 10 years for which data were analyzed showed an ecological deficit, and the overall ecological security situation was very weak and unsustainable. Pasture is the main resource for consumption in ecological footprint evaluation in Maqu County, and the imbalance between demand for pasture forage for consumption and sustainable supply, with resulting pasture degradation, is strongly evident. Therefore the protection of grassland through adoption of ecologically sustainable practice in this area should become apriority.

Differences in vegetation community structure in hot-dry valleys in Yunnan Province related to valley stability

HE Zhou-yao, WANG Yong, SU Zheng-an, YANG Hong-kun, ZHOU Tao

2020, 29(9):  28-37.  DOI: 10.11686/cyxb2019529

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In this research, field surveys of species composition and vegetation community structure of 22 gullies in the hot-dry valley region of Yuanmou County in Yunnan Province were carried out using standard vegetation sampling methods to study the plant community structure in gullies with different activity levels. As the gully stability increased, the number of plant species also increased. Twenty-eight species of plants belonging to 28 genera of 12 families, were found in active gullies. Twenty-nine species of plants belonging to 29 genera of 16 families, were found in semi-stable gullies. Thirty-seven species of plants belonging to 35 genera of 15 families were discovered in stable gullies. Based on plant form, the gully vegetation communities could be divided into three layers (herb layer, shrub layer and tree layer) which varied with the activity level of the gullies. No tree layer was found in the active gullies. The dominant species in the herb layer was Heteropogon contortus, with Bothriochloa pertusa and Aristida adscensionis as sub-dominant species. The dominant species in the shrub layer was Dodonaea viscosa, with Leucaena leucocephala as the sub-dominant species. The dominant species of the tree layer was Azadirachta Indica, with Eucalyptus robusta as the sub-dominant species. As the gully stability increased, so also did the coverage of its vegetation community. The plant communities in gullies with differing activity levels were all dominated by perennial herbs and shrubs, with a smaller number of tree species of trees, in which the dominant species were the same and played similar roles in the plant communities. However, with increasing stability of gullies, the number and diversity of trees gradually increased. For active gullies, semi-stable gullies and stable gullies, the plant community similarities were comparatively similar in the herb layer, extremely similar in the shrub layer, and extremely different in the tree layer. As the stability of a gully changed, the tendency for the plant community matured without species change in the shrub layer was evident. However, for the herb layer and tree layer, as the gully stability increased with time the species composition of the vegetation community evolved. These results indicate that the activity status of a gully plays an important role in determining the community structure of the tree layers, while the community structure of the shrub layer was less affected by the activity status of the gully. In summary, an obvious difference in vegetation structure was evident between gullies with different activity status, and this information could provide a scientific basis for gully ecological restoration decisions and for formulation of future studies.

The response of vegetation community structure and biomass in Stipa breviflora desert steppe to water and nitrogen

LI Jing, HONG Mei, YAN Jin, ZHANG Yu-chen, LIANG Zhi-wei, YE He, GAO Hai-yan, ZHAO Bayinnamula

2020, 29(9):  38-48.  DOI: 10.11686/cyxb2019516

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An experiment comprising a factorial combination of three water and four nitrogen levels (12 treatments), laid out in a split plot design, was conducted to understand the effects of precipitation change and nitrogen deposition on vegetation community structure and biomass in Stipa breviflora desert steppe in Siziwang Banner, Inner Mongolia. The main plot treatments were: CK (natural rainfall), W (30% rainfall addition), R (30% rainfall reduction), while the subplot treatments were 0 (N₀), 30 (N₃₀), 50 (N₅₀), and 100 (N₁₀₀) kg N·ha^-1·a^-1. The results show: 1) The application of water and nitrogen resulted in significant changes in community composition and species importance values. The R treatment had the lowest number of community species, and the importance value of dominant species in community was increased. The addition of nitrogen resulted in a curve of ‘parabola’ shape for number of species present (i.e. the number of community species was higher at medium nitrogen application rates than at N₀ or N₁₀₀). 2) With increased rate of nitrogen addition, species richness, Shannon-wiener diversity and Pielou evenness index were initially increased, but decreased at higher nitrogen application rates. The maximum values were observed in treatments CK-N₃₀, W-N₃₀ and R-N₅₀ in 2016 and 2018, and the lowest value of CK-N₃₀, W-N₃₀, R-N₅₀ in the drought year (2017), respectively. The main effects of water, nitrogen and water-nitrogen interaction all have significant effects on the above three plant diversity indexes (P<0.05). 3) Water and nitrogen both stimulated aboveground biomass increase. Water, nitrogen as well as water and nitrogen interaction have significant effects on aboveground biomass (P<0.05). The proportion of perennial grasses in the total aboveground biomass was increased by short-term nitrogen addition, while the percentage of perennial weeds was decreased.

C, N and P ecological stoichiometry characteristics of a Stipa species plant-soil system subject to grazing exclusion in a desert steppe

WAN Fang, MENG Zhong-ju, DANG Xiao-hong, WANG Rui-dong, ZHANG Hui-min

2020, 29(9):  49-55.  DOI: 10.11686/cyxb2019523

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This research was conducted at Xilamuren in Inner Mongolia on typical desert steppe grassland dominated by Stipa breviflora and Stipa krylovii with the objective of defining the C, N, and P stoichiometry of leaves, litter and soil under two management regimes (year-round grazing exclusion and seasonal grazing exclusion). It was found that: 1) The content of C, N and P in the leaves and litter in year-round exclusion were all greater than in the seasonal exclusion, while the content of soil N in year-round exclusion (2.54 g·kg^-1) was less than that in the seasonal exclusion (2.75 g·kg^-1). 2) The C∶N and C∶P ratios of the leaves in seasonal exclusion was greater than that in the year-round exclusion, which showed that the carbon sequestration ability of the two grasses was reduced under year-round exclusion. However, the soil C∶N and C∶P ratios in seasonal exclusion (4.92 and 36.58, respectively) were less (P<0.05) than those in year-round exclusion (6.03 and 39.80, respectively). 3) The N∶P ratio of leaves were typically greater than 16. Therefore, this is an obvious indication that the two grasses studied were mainly restricted by lack of P at the study site. These results provide scientific data assist decisions on the sustainable recovery management of the desert grassland.

Effects of short-term non-grazing on soil nutrients in Haloxylon persicum desert and Anabasis salsa desert

Bieerdawulieti·XIHAYI, DONG Yi-qiang, AN Sha-zhou, WEI Peng

2020, 29(9):  56-62.  DOI: 10.11686/cyxb2019496

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This research aims to clarify the effects of un-grazing (UG) on the nutrients composition of soil in Anabasis salsa desert (6 years of enclosure) and Haloxylon persicum desert (7 years of enclosure) and use the method of combination field survey with the laboratory analysis and studied the response of desert the nutrients composition of soil, which provide a scientific basis and management for the local animal husbandry. The results showed that: 1) The soil nutrient concentrations in A. salsa desert were significantly higher than in the H. persicum desert. 2) In A. salsa desert, short-term grazing exclusion (GE) had little effect on the carbon density, total N, total P and total K of the soil system. 3) In H. persicum desert, the carbon density increased by 43.46% (P>0.05) with GE, but total P and total K were decreased by 33.53% (P<0.05) and 60.30% (P<0.05), respectively. In summary, short-term GE has a small effect on soil properties in A. salsa desert, and promoted increased soil carbon density in H. persicum desert, but led to a decline in the total P and total K in H. persicum desert. The results showed that the GE effect differs between desert vegetation types and soil types.

Effects of grazing exclosure and herbicide on soil physical-chemical properties and microbial biomass of Stellera chamaejasme patches in degraded grassland

BAO Gen-sheng, SONG Mei-ling, WANG Yu-qin, YIN Ya-li, WANG Hong-sheng

2020, 29(9):  63-72.  DOI: 10.11686/cyxb2019560

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Stellera chamaejasme is a toxic plant, largely distributed in degraded grassland of the Qinghai-Tibetan Plateau, where it can dominate other vegetation. Grazing exclosure and herbicides are considered the effective methods to control S. chamaejasme and restore degraded grassland where S. chamaejasme has become the dominant species. However, effects of grazing exclosure and herbicides on plant community structure, soil physical-chemical properties and soil microbial biomass within or between patches of S. chamaejasme are unclear. Therefore, plant diversity indexes, soil nutrient status, and soil microbial biomass were determined within and between S. chamaejasme patches after one year of grazing exclosure and herbicide application. It was found that aboveground biomass and plant diversity indexes within natural patches of S. chamaejasme were higher than between patches; however, aboveground biomass within herbicide application patches was lower than between them. In the surface soil (0-10 cm), Stellera increased soil moisture content, total nitrogen, ammonium, nitrate and organic matter. By contrast, herbicide decreased the organic matter and total potassium within patches. At greater soil depth (10-20 cm), Stellera increased ammonium and nitrate content; in contrast, herbicide decreased available phosphorus, ammonium and organic matter. Herbicide and grazing exclosure increased microbial carbon biomass within patches compared with between patches. Furthermore, herbicide increased soil microbial nitrogen biomass but decreased microbial phosphorus within patches. Combing herbicide and grazing exclosure decreased the S. chamaejasme population, improved grass biomass, regulated plant community structure and accelerated nutrient cycling, and resulted in restoration of the degraded grassland in which S. chamaejasme had become the dominant species.

Shrub encroachment effects on the stability of soil aggregates and the differentiation of Fe and Al oxides in Qinghai-Tibet alpine grassland

CHEN Hong, MA Wen-ming, ZHOU Qing-ping, YANG Zhi, LIU Chao-wen, LIU Jin-qiu, DU Zhong-man

2020, 29(9):  73-84.  DOI: 10.11686/cyxb2020065

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The physical protection of soil aggregates is an important mechanism of soil carbon sequestration. In this study, shrub-grassland and shrubless-grassland in East margin of Qinghai-Tibet Plateau were investigated. We used wet sieving proposed by Cambardella and Elliott and a settling siphon to separate soil aggregates, which were then measured. Data obtained included: Soil aggregate stability, differentiation of different forms of Fe and Al oxides, and the relationship between Fe and Al oxides and soil aggregate stability. It was found that: Shrub encroachment significantly reduced (P<0.05) the proportion of microaggregates (<0.053 mm), but had no significant effect on soil aggregate stability (P>0.05). Shrub encroachment significantly increased the content of dithionthite-citrate-bicarbonate extractable Al oxides in macroaggregates (>0.25 mm), which was increased by 14.09% (P<0.05). Shrub encroachment also significantly increased the content of dithionthite-citrate-bicarbonate extractable Fe and Al oxides in microaggregates (<0.25 mm), which was increased by 9.75% and 15.31%, respectively (P<0.05). However, shrub encroachment significantly reduced the content of complex Fe and Al oxides in microaggregates (<0.25 mm), the content of sodium pyrophosphate extractable Fe and Al oxides decreased by 31.03% and 9.41%, respectively (P<0.05). Boosted regression tree analysis indicated that the free Fe and Al oxides had the strongest effect on soil aggregate stability, while the complex Al oxides had the weakest effect.The results indicate that shrub encroachment is helpful to enhance soil aggregate stability and promote the sequestration of soil organic carbon.

Comprehensive evaluation of effects of fertilization on grassland quality index and soil properties in alpine steppe

GUO Jian-bo, ZHAO Guo-qiang, JIA Shu-gang, DONG Jun-fu, CHEN Long, WANG Shu-ping

2020, 29(9):  85-93.  DOI: 10.11686/cyxb2019513

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This research investigated the effects of fertilization on degraded alpine steppe in the Tibetan Plateau, and aimed to comprehensively assess the quality of this alpine grassland based on the index of grassland quality (IGQ) and soil properties. A field experiment was conducted in Bange County with three different N and four different P fertilization levels [N: 0 (N₀), 7.5 (N₁), 15.0 (N₂) g N·m^-2; P: 0 (P₀), 7.5 (P₁), 15.0 (P₂), 30.0 (P₃) g P₂O₅·m^-2] in a factorial combination, with 12 N-P combinations, and N₀P₀ as control. The aboveground biomass of different vegetation communities and soil physical and chemical properties were assessed within the controlled experiment. It was found that combined application of nitrogen and phosphorus improved the IGQ, but only the treatment N₁P₁ (N: 7.5 g N·m^-2, P: 7.5 g P₂O₅·m^-2) had a significant effect on IGQ, which under tis treatment was increased by 67.16% compared with control. Data for soil organic matter, total nitrogen and phosphorus, available nitrogen and phosphorus, and pH under the 12 different treatments for three soil depths (0-10 cm, 10-20 cm, 20-30 cm) were subjected to principal component analysis. The results showed that soil pH is negatively correlated with total nitrogen and available nitrogen, and fertilization had a greater impact on soil quality in the 0-10 cm soil layer than in the 10-20 cm and 20-30 cm soil layers. The high P level (30.0 g P₂O₅·m^-2) of fertilizer application increased soil total phosphorus and available phosphorus content but had an adverse effect on plant absorption rate. In summary, N : P fertilization (except treatments N₀P₁, N₁P₀) improved grassland quality, and N₁P₁ had the highest relative score. Hence, moderate N : P fertilization plays a positive role in improving grassland quality and soil fertility in the alpine steppe on the Tibetan Plateau. Further study is necessary to understand the restoration effect of manure.

A data envelopment analysis study of alfalfa fertilization responses and economic return in the desert irrigation area of Hexi

WU Yong, LIU Xiao-jing, LIN Fang, TONG Chang-chun

2020, 29(9):  94-105.  DOI: 10.11686/cyxb2019504

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This study quantitatively assessed the effects of various fertilization regimes on the herbage quality and yield of ‘Gannong No.3’ alfalfa in the main production areas of the Hexi Corridor. In a field experiment conducted in 2016 and 2017, a balanced fertilization regime (N 103.5 kg·ha^-1, P₂O₅ 105 kg·ha^-1, K₂O 90 kg·ha^-1) recommended for alfalfa forage production this area was used as a control and compared with nil fertilization, or with a suboptimal level of one of the three elements, N, P or K, and economic benefit was analyzed by data envelopment analysis (DEA). It was found that compared with no fertilization, all fertilizer treatments significantly increased alfalfa yield and total protein content, reduced the acid and neutral detergent fiber levels, improved relative feeding value, and increased the economic benefit. Compared with balanced fertilization, yield and quality of alfalfa herbage of treatments receiving the suboptimal fertilizer regimes were significantly lower than those of the balanced fertilization treatment, especially in the case of suboptimal P application. In 2016 and 2017, the total yield decreased by 25.9% and 25.7%, respectively, and the total protein concentration by 33.4%, 33.1%, respectively, relative to balanced fertilization, on the suboptimal P treatment. These results demonstrate that phosphorus is the nutrient limiting factor for alfalfa forage production in the desert irrigation area of Hexi, and that the importance-ranking of the three tested fertilizer elements is P>N>K. Analysis of the results using DEA showed that balanced fertilization gave the highest economic return (10679 CNY·ha^-1), while the nil fertilization treatment gave the lowest, and the treatments with suboptimal N, P or K were intermediate and ranked: Partial phosphorus deficiency<partial nitrogen deficiency<partial potassium deficiency.

Effects of mixing ratio and nitrogen fertilization on root characteristics in the common vetch/oat mixture

WU Xiao-juan, YANG Mei, LU Yi-xiao, YANG Hui-min

2020, 29(9):  106-116.  DOI: 10.11686/cyxb2020014

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Legume-grass mixtures are common in cultivated grasslands, and such mixtures can significantly improve soil fertility and enhance the natural productivity. Root litter is an important source of soil organic matter, but the reciprocal impact of each species on the root characteristics of the other species in forage mixtures is still not clear. The reciprocal impacts on root biomass and root traits in mixtures comprising common vetch and oats were studied under different nitrogen fertilizer levels and ratios of plant numbers of the two species in the mixture (mixing ratios) or in pure stands. 1) There were significant interactions between mixing ratio and nitrogen fertilization for root biomass and root traits. Root biomass values of the mixtures were significantly greater than those of the monocultures. Root biomass was greater at low and medium fertilization levels, than at high fertilization levels. There was an inhibition effect of high nitrogen fertilizer on root length, specific root length, root surface area and specific root area in the early stages of plant development, and the inhibition effect decreased with increase in common vetch proportion in the mixtures in the later stages of plant development. 2) The content of nitrate nitrogen in the mixtures was greater than that in the monocultures, but the content of ammonium nitrogen in the mixtures was greater than that in the monocultures only at the milk stage of grain development. The content of mineral nitrogen increased with the increase in common vetch proportion. Nitrogen fertilization significantly affected mineral nitrogen content in 0-30 cm soil layers and was highest under 100 kg·ha^-1 nitrogen fertilization, and lowest without nitrogen fertilization. 3) There was a significant positive correlation between soil nitrate nitrogen content and root biomass, and there were significant negative correlations with root length, root surface area and root volume. In summary, increase in the common vetch proportion in the mixtures was helpful to improve soil the mineral nitrogen of soil and optimize the root traits of the mixed stands of common vetch and oats.

Response of stem characteristics and yield to sowing rate in soybean

YU Xiao-bo, LIANG Jian-qiu, HE Ze-min, ZHOU Quan-lu, WU Hai-ying, ZHANG Ming-rong

2020, 29(9):  117-124.  DOI: 10.11686/cyxb2019514

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Two soybean varieties, Nandou12 (ND₁₂) and Nandou25 (ND₂₅), with different 100-seed weight and growth characteristics were used in field experiment to investigate the maturation rate, stem growth characteristics and yield at different sowing rates. It was found that seedling density of ND₁₂ was higher than that of ND₂₅ with the same sowing rate, but the mature plant number of ND₁₂ was lower and the maturation rate was slower than for ND₂₅. The variety×sowing rate interaction effect for mature plant number was significant. With increased sowing rate, stem diameter decreased significantly. However, stem height, height of the stem center of gravity and internode length increased significantly. Elongation growth of the stem was promoted, but increase in stem diameter was restrained. ND₂₅ was more sensitive to increase in plant density than ND₁₂. ND₁₂ had a higher reduction in seed number per plant with increased plant density than ND₂₅, but a lower reduction in 100-seed weight. The plant density response of various yield components differed between varieties. As the sowing rate and mature plant number increased, the stem mechanical strength and lodging resistance index decreased, while yield increased initially and then decreased. There was no significant difference between varieties for plant seed weight while the effect of density on yield formation was more important than that of lodging. ND₁₂ and ND₂₅ have the highest yield at 90 and 120 kg·ha^-1, respectively.

Role of grain crushing resistance and grain threshing characteristics in determining suitability of feed maize cultivars for machine harvesting and effect of plant moisture content

LEI En, SHAO Di, ZHU Tian-biao, SHU Xing, YANG Yong-bing, WANG Yue-dong, TANG Qi-yuan

2020, 29(9):  125-135.  DOI: 10.11686/cyxb2019517

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This research studied the role of selected mechanical properties of grain and cob (in particular grain crushing resistance and the detachment resistance of grain on the cob) and plant and cob moisture content in determining suitability for machine harvesting in feed maize. This information is important for improving harvest outcomes for feed maize crops in Southwest China. An early and a late maturing cultivar were tested. The experiment involved a mechanical harvester and a large field study. It was found that the grain crushing resistance (CR, force required to crush grains) and detachment resistance (DR, force required to detach grains from the cob) directly affected the percentage of broken grain (%BG). The relationship between %BG and CR could be described by the quadratic regression relationship: $\overline{\%BG}$=0.0021CR²-1.5443CR+293.78 (R²=0.8827, P<0.001), and the relationship between %BG and DR by a power regression relationship: $\overline{\%BG}$=0.007DR^4.12 (R²=0.7656, P<0.001). The relationship between %BG and crushing resistance of the cobs was much lower than the aforementioned (R²=0.1644, 0.01<P<0.05). In the later stages of maturation, although the DR of early maturing cultivar ‘JY99’ was significantly lower than that of late maturing cultivar ‘BY9’, the grain crushing strength of ‘BY9’ was significantly higher than that of ‘JY99’, so that these two factors cancelled each other, leading to there being no significant difference in %BG between the two cultivars. In addition to these relationships there was also an association between plant lodging and grain loss; the stripper rotor of the header harvester readily caused grain loss before ear threshing. Further, the grain loss was greater when grains were easy to thresh. Overall, grain impurity rate significantly declined as the water content of the non grain organs reduced. A maize cultivar suitable for mechanical grain harvesting should possess specific characteristics, including tough stalks that are resistant to lodging, with grains that are hard and easily detachable.

Effect of mixed inoculation of Glomus mosseae and Sinorhizobium melilotion alkali resistance of alfalfa

XING Yi-mei, DONG Li, ZHAN Li-feng, CAI Hua, YANG Sheng-qiu, SUN Na

2020, 29(9):  136-145.  DOI: 10.11686/cyxb2019509

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Alfalfa is a perennial legume with high forage yield and quality that plays an important role in eco-environment improvement and cropping rotations. However, land salinization seriously inhibits the normal growth and development of alfalfa. Arbuscular mycorrhizal fungi (AMF) and rhizobia (R) are common symbiotic soil microorganisms. They can coexist with legumes such as alfalfa, and form a symbiotic system comprising AMF-alfalfa-R. In this study, we inoculated alfalfa with Glomus mosseae and Sinorhizobium meliloti, and compared the alkali resistance of plants with inoculum combinations. It was found that without alkali stress, the growth of G. mosseae-inoculated plants or R-inoculated plants was higher than that of non-inoculated (NI) ones. Important differences included higher chlorophyll content, relatively longer root length, higher plant height, and increased branch number. With alkali stress treatment, the growth of each group was inhibited in different ways, but the inoculated groups again showed higher alkali tolerance than NI. Compared with NI, the malondialdehyde content and relative conductivity remained at a low level in the NI group. The relative water content of the cells was higher, as were the activities of superoxide dismutase, peroxidase and catalase. Based on these results, single inoculation and mixed inoculation can both improve the osmotic adjustment ability and antioxidant capacity of alfalfa, and reduce damage to the cell membrane, but the results of mixed inoculation is even better.

Effects of exogenous 2, 4-epibrassinolide on the growth and photosynthesis of alfalfa under high temperature and low light stress in summer

QIN Feng-fei, LI Zhi-hua, LIU Xin-bao, QU Hui, PINGCUO Zhuo-ma, LUOSONG Qun-cuo, SU Meng-han

2020, 29(9):  146-160.  DOI: 10.11686/cyxb2019511

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This study investigated the regulatory effects of exogenous 2, 4-epibrassinolide (EBR) on the growth and photosynthesis of alfalfa under high temperature and low light stress in summer. A simulated shade experiment with green shade mesh was conducted by setting up three light environments [full sunlight (L₀), 46.30% sunlight (L₁), and 28.63% sunlight] and four EBR concentrations [distilled water (CK), 0.01, 0.1, and 1 mg·L^-1]. The effects of EBR on the morphology, growth, photosynthetic pigment content, photosynthetic parameters and photosynthetic light-response curve were assessed. Results showed that the photosynthetically active radiation (PAR), red to far-red (R∶FR) ratio and percentages of the red and violet bands in PAR on the alfalfa canopy significantly decreased and that the percentage of the green band significantly increased with increasing shade in summer. Compared with CK, the leaf area, leaf mass rate, internode length, acropetal angles between leaf and mainstem, chlorophyll a and b contents, and intercellular CO₂ concentration significantly increased, and temperature of the leaf thermocouple (T_leaf) and carotenoid content significantly decreased under shaded conditions. Compared with L₀, the net photosynthetic rate and maximum net photosynthetic rate did not show distinct changes with 1 mg·L^-1 EBR treatment under L₁ in summer. The results of Pearson correlation analysis showed that PAR, R∶FR, and the percentage of the violet band on the alfalfa canopy had significant positive correlations with light intensity under shaded conditions. The root mass rate had a distinctly negative correlation, and the node number of the mainstem had no significant correlation with light intensity under EBR or shade treatments. The above results indicate that exogenous EBR can regulate the plant structure, decrease T_leaf, promote the synthesis of photosynthetic pigments, and improve the photosynthetic efficiency, and in this way alleviate high temperature and low light stress in alfalfa. Among the rates tested, 1 mg·L^-1of EBR was the optimal concentration to improve the growth of alfalfa under slight shading (L₁) during the summer period.

Allelopathic effects of extracts of Vicia villosa on the germination of four forage seeds

NIU Huan-huan, WANG Sen-sen, JIA Hong-ding, CHEN Gui-hua

2020, 29(9):  161-168.  DOI: 10.11686/cyxb2020003

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This research used a bioassay method to evaluate the effects of a range of concentrations (2.5, 5.0, 10.0, 20.0, 40.0 g·L^-1) of extracts of aboveground and underground parts of Vicia villosa on seed germination of four important forage species: Avena sativa, Lolium multiflorum, Medicago sativa and Trifolium repens. The results showed that in the concentration range tested, the V. villosa extracts of aboveground parts significantly inhibited the seed germination of M. sativa and T. repens. The inhibitory effect of T. repens increased with increasing concentration and the germination rate of T. repens seeds reduced by 62.5% compared with the control under the 40 g·L^-1 treatment. The extract of underground parts of V. villosa inhibited the root length of L. multiflorum, M. sativa and T. repens. Among the tested species, the M. sativa root length under 40 g·L^-1 treatment displayed the largest inhibitory effect (64.94%) compared with the control. With respect to the effects of the underground extract on seedling heights, the height of M. sativa seedlings under the 40 g·L^-1 treatment was significantly reduced, compared to the control. In some cases, the extracts reduced the chlorophyll content of L. multiflorum, M. sativa and T. repens. However, for A. sativa, treated with underground extracts at 20 g·L^-1, the chlorophyll content was increased by 144.23% compared to the control. Treatment with the underground extract significantly increased the peroxidase activity of M. sativa and T. repens. Treatment with the aboveground and underground extract of V. villosa enhanced the catalase (CAT) activity of T. repens and decreased the CAT activity of M. sativa.

A study of the allelopathic effect of extracts from different parts of Iva xanthiifolia on five native species

LI Feng-lan, WU Jia-wen, YAO Shu-kuan, ZHAO Zi-yi, ZHAO Xiao-can, HE Fu-meng, ZHU Yuan-fang, SHI Qi-hai, ZHOU Lei, XU Yong-qing

2020, 29(9):  169-178.  DOI: 10.11686/cyxb2019533

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This research explored the allelopathic effects of extracts of the exotic plant Iva xanthiifolia on seed germination and seedling growth of native plants. Seeds of five native plant species were treated with water extracts of the plant. The extracts from different parts of I. xanthiifolia had different allelopathic effects, with the suppression effect of leaf extract being the strongest. Among the acid, alkaline and neutral components isolated from leaves, the allelopathic effect of the neutral group was stronger than that of the acid and alkaline components. The sensitivity of different native plants treated with the same extract of I. xanthiifolia was also different. The seed germination and seedling growth of Setaria viridis and Amaranthus tricolor were sensitive to the extracts from different parts of I. xanthiifolia. Low concentration of the extract promoted the growth of Artemisia sieversiana, Echinochloa crusgalli and Chenopodium album, while a high concentration of the extract inhibited the growth of the same three species.

Effects of fresh feeding Fagopyrum dibotrys on performance, egg quality and serum index of heat stressed laying hens

ZHANG Rong, CHEN Guang-ji, SHANG Yi-shun, LI Shi-ge, LI Xiao-dong, XIONG Xian-qin, MU Qiong, WANG Xiao-li, RAN Wei-nan, BAN Song-zhi

2020, 29(9):  179-189.  DOI: 10.11686/cyxb2020080

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The objective of this research was to determine the effects on laying performance, egg quality and serum hormone levels, of feeding fresh Fagopyrum dibotrys as part of the diet of Changshun Blue-Eggshell laying hens. Laying hens (n=300) were divided into five treatment groups with a completely randomized design: Control (group C, basic diet), T₁ (basic diet+5% F. dibotrys), T₂ (basic diet+10% F. dibotrys), T₃ (basic diet+15% F. dibotrys) and T₄ (basic diet+20% F. dibotrys), with 5 replicates per treatment and 12 chickens per replicate. All experimental laying hens were exposed to (31.4±1.5) ℃ to induce natural heat stress. Data collected included: The average monthly feed intake, egg weight and number of the laying eggs, the apparent quality of eggs, the content of amino acids and fatty acids in the whole egg, the levels of serum hormones, inflammatory factors and endotoxin concentration at the end of the experiment. It was found that: 1) The laying rate of the T₁ group in the second month was significantly higher than that of other groups (P<0.05), and there was no significant difference between the laying rates of groups C, T₁ and T₂ in the third month and the whole period (P>0.05). 2) The egg content of isoleucine was the highest in T₃ group, but higher in T₃ and T₄ groups than the others (P<0.05), but the polyunsaturated fatty acids in group C were significantly higher than those in other treatment groups (P<0.05). 3) The concentrations of adrenocorticotropic hormone and corticosterone in group C were significantly higher than those in the experimental groups (P<0.05); conversely, the levels of corticosterone and luteinizing hormone in group C were significantly lower than those in the experimental group (P<0.05), and the levels of IL-6, tumor necrosis factor α and serum endotoxin in the experimental group were significantly lower than those in the control group (P<0.05). Thus, it was found that adding 10% F. dibotrys to the diet had no negative effect on the average egg production rate, deepened the yolk color, improved the amino acid composition and content of the whole egg, but had a negative effect on the fatty acid composition of the yolk, increased the serum FSH and LH content, and reduced the serum inflammatory factor and endotoxin level.

Transcriptome analysis of Tilletia horrida at different infection time points

SHU Xin-yue, JIANG Bo, MA Li, ZHENG Ai-ping

2020, 29(9):  190-202.  DOI: 10.11686/cyxb2019505

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Rice kernel smut (RSB) caused by Tilletia horrida, is one of the most important rice diseases in hybrid rice growing areas worldwide. In order to classify the mechanisms of pathogenicity, transcriptome analysis of the T. horrid strain JY-521 was conducted at different times post inoculation (8, 12, 24, 48, and 72 h) early in the infection. The highest number of differentially expressed genes (DEGs) occurred at 8 h post inoculation. Based on kyoto encyclopedia of genes and genomes (KEGG) pathway analysis of the DEGs, autophagy processes and lipid degradation were key pathways for T. horrida pathogenicity. The expression patterns of carbohydrate-active enzyme genes, pathogen-host interaction genes, and secreted protein genes were also analyzed at different times during the infection, and some DEGs that may play an important role in pathogenic progress of T. horrid were found. In summary, this research provides a new foundation for future study of the infection mechanism and control of this important rice disease.

Research progress on plant architecture formation and forage grass plant architecture

ZHANG Yu-tong, SHI Feng-ling

2020, 29(9):  203-214.  DOI: 10.11686/cyxb2020083

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Forage grass breeding is an important foundation for sustainable development of forage industries. At present, in addition to conventional breeding methods, molecular breeding methods have also made some breakthroughs, especially in breeding for stress resistance. Plant architecture is an important agronomic trait of plants, and it is an important trait that affects plant colony structure and yield formation. Historically, the molecular mechanisms and regulatory networks of plant architecture in annual crops have been systematically studied, but there are fewer studies on the mechanisms governing plant architecture in forage grasses. Most of the extant studies deal with yield-related traits and basic molecular breeding. In this paper, the factors influencing the formation of plant architecture and their mechanism are summarized, and the research progress in forage grass plant architecture traits is reviewed. Lastly, the current key issues in forage plant architecture research and breeding are briefly reviewed, and some suggestions are put forward. It is concluded that the research strategy for forage plant architecture modification through breeding can be developed by referring to the frontier research directions of the crop of interest.