套作对大豆苗期碳氮物质代谢的影响及其与抗倒伏性的关系

为从植株光形态建成的角度,阐明玉米-大豆套作模式下,大豆苗期倒伏发生的原因。在大豆单作和玉米-大豆套作两种种植模式下,以强耐阴大豆南豆12和弱耐阴大豆南032-4为试验材料,对大豆倒伏率、茎秆形态、叶片光合特性,茎秆和叶片碳氮代谢物质含量等进行调查、测定和分析。结果表明,由于套作受共生期内玉米的遮阴,大豆处于弱光环境,导致植株形态发生改变,光合速率降低,并发生倒伏,但两种大豆品种受荫蔽影响的程度不同。南豆12受荫蔽的影响较小,倒伏率显著低于南032-4,茎秆长粗比增加幅度和光合速率降低幅度也显著低于南032-4,相关分析表明,倒伏率与茎秆长粗比呈极显著正相关(r=0.946;P<0.01);与叶片光合速率呈显著负相关(r=-0.886;P<0.05);叶片光合速率与光合有效辐射呈极显著正相关(r=0.900;P<0.01),说明套作荫蔽降低了大豆冠层的光合有效辐射而导致大豆叶片光合速率降低是引起套作大豆形态改变,发生倒伏的重要原因;分析大豆叶片光合速率、茎秆碳氮比、叶片碳氮比和倒伏率发现,套作显著降低了茎秆和叶片碳氮比,降低幅度表现为南032-4显著高于南豆12,相关分析表明,叶片光合速率与茎秆和叶片碳氮比呈显著或极显著负相关(r=-0.871,-0.930;P<0.05),茎秆和叶片碳氮比与倒伏率呈极显著正相关(r=0.985,0.968;P<0.01),说明较高的碳氮比是南豆12具有较强抗倒伏能力的生理基础,使其能够在套作环境下维持较优的光形态特性,更适合于套作种植;分析大豆碳氮物质代谢可知,套作显著降低了大豆茎秆和叶片的碳氮代谢物质含量,不同品种间表现为南豆12显著高于南032-4。说明较高的碳氮代谢活性和光合产物运输能力是增强套作大豆抗倒伏能力的物质基础和代谢基础。以玉米-大豆带状套作种植为对象,探明了套作大豆植株倒伏与茎叶碳氮代谢物质转运的关系,为培育套作专用的耐阴抗倒伏大豆品种提供理论支持。

套作对大豆苗期茎秆纤维素合成相关糖类物质转化的影响及其与叶片光合的关系

【目的】从纤维素合成相关糖类物质转化的角度,阐明玉米大豆套作模式下,大豆苗期茎秆光形态建成的机理。【方法】在大豆单作和玉米大豆套作两种种植模式下,以强耐荫大豆南豆12和弱耐荫大豆南032-4为试验材料,对叶片光合速率和茎秆总碳、纤维素、可溶性糖、蔗糖、β-1,3-葡聚糖等含量进行测定和分析。【结果】与单作相比,套作大豆由于受到玉米荫蔽,苗期光合速率显著降低,但材料间对套作的反应程度不同,强耐荫大豆南豆12受套作荫蔽的影响程度相对较小,在套作下表现出较强的光合能力;套作显著降低了大豆叶片和茎秆的总碳含量,但南豆12的降低幅度显著低于南032-4。相关分析表明叶片光合速率与叶片和茎秆的总碳含量、茎秆的纤维素含量均呈极显著正相关(r=0.952,0.935,0.825,P<0.01),说明荫蔽通过影响大豆叶片的光合速率,减少了光合产物的积累和向茎秆中的分配,导致大豆植株茎秆纤维素含量降低;强耐荫大豆南豆12在荫蔽下的光合速率较高,光合产物积累较多,适合套作种植。在整个苗期,虽然套作大豆茎秆可溶性糖含量均显著低于单作,但β-1,3-葡聚糖和蔗糖含量在大豆出苗后30—51 d却表现为套作显著高于单作,且在套作模式下,两个大豆糖类物质转化率差异显著;同一种植模式下,强耐荫大豆南豆12茎秆可溶性糖、蔗糖和β-1,3-葡聚糖的含量和转化率均显著或极显著高于南032-4。对纤维素沉积方式分析表明,同一大豆材料,单作模式下茎秆纤维素快速累积时间和累积速率要高于套作;同一种植模式下,强耐荫大豆南豆12纤维素快速累积时间要短于南032-4,但差异较小,而累积速率要高于南032-4,最终导致南豆12的茎秆纤维素含量显著高于南032-4。【结论】套作荫蔽降低了大豆叶片的光合能力,减少了光合产物向茎秆的运输量和茎秆填充物的含量,改变了茎秆纤维素的沉积方式,使得纤维素的含量降低;而强耐荫性大豆南豆12在套作模式下能保持较高光合能力和茎秆纤维素合成能力,具有较强的抗倒伏性。

Crop photosynthetic response to light quality and light intensity

Under natural conditions, plants constantly encounter various biotic and abiotic factors, which can potentially restrict plant growth and development and even limit crop productivity. Among various abiotic factors affecting plant photosynthesis, light serves as an important factor that drives carbon metabolism in plants and supports life on earth. The two components of light(light quality and light intensity) greatly affect plant photosynthesis and other plant's morphological, physiological and biochemical parameters. The response of plants to different spectral radiations and intensities differs in various species and also depends on growing conditions. To date, much research has been conducted regarding how different spectral radiations of varying intensity can affect plant growth and development. This review is an effort to briefly summarize the available information on the effects of light components on various plant parameters such as stem and leaf morphology and anatomy, stomatal development, photosynthetic apparatus, pigment composition, reactive oxygen species(ROS) production, antioxidants, and hormone production.

Shade stress decreases stem strength of soybean through restraining lignin biosynthesis

Lodging is the most important constraint for soybean growth at seedling stage in maize-soybean relay strip intercropping system.In the field experiments,three soybean cultivars Nandou 032-4(shade susceptible cultivar; B1),Jiuyuehuang(moderately shade tolerant cultivar; B2),and Nandou 12(shade tolerant cultivar; B3) were used to evaluate the relationship between stem stress and lignin metabolism in the stem of soybean.Results showed that the intercropped soybean was in variable light condition throughout the day time and co-growth stage with maize.The xylem area and cross section ratio played a main role to form the stem stress.The B3 both in intercropping and monocropping expressed a high stem stress with higher xylem area,lignin content,and activity of enzymes(phenylalanine ammonia-lyase(PAL),4-coumarate: CoA ligase(4CL),cinnamyl alcohol dehydrogenase(CAD),and peroxidase(POD)) than those of B1 and B2.Among the soybean cultivars and planting pattern,lignin content was positively correlated with stem stress.However,a negative correlation was found between lignin content and actual rate of lodging.In conclusion,the shade tolerant soybean cultivar had larger xylem area,higher lignin content and activities of CAD,4CL,PAL,and POD than other soybean cultivars in intercropping.The lodging in maize-soybean intercropping can be minimized by planting shade tolerant and lodging resistant cultivar of soybean.The lignin content in stem could be a useful indicator for the evaluation of lodging resistance of soybean in intercropping and activities of enzymes were the key factors that influence the lignin biosynthesis.

Effect of shade stress on lignin biosynthesis in soybean stems

To clarify how shade stress affects lignin biosynthesis in soybean stem, two varieties, Nandou 12（shade tolerant） and Nan 032-4（shade susceptible） grew under normal light and shade conditions（the photosynthetically active radiation and the ratio of red：far-red were lower than normal light condition）. Lignin accumulation, transcripts of genes involved in lignin biosynthesis, and intermediates content of lignin biosynthesis were analyzed. Both soybean varieties suffered shade stress had increased plant heights and internode lengths, and reduced stem diameters and lignin accumulation in stems. The expression levels of lignin-related genes were significantly influenced by shade stress, with interactions between the light environment and variety. The gene of 3-hydroxylase（C3H）, cinnamoyl-Co A reductase（CCR）, caffeoylCoAO-methyltransferase（CCoAOMT）, and peroxidase（POD） attributed to lignin biosynthesis under shade stress, and the down-regulation of these genes resulted in lower caffeic, sinapic, and ferulic acid levels, which caused a further decrease in lignin biosynthesis. Under shade stress, the shade tolerant soybean variety（Nandou 12） showed stiffer stems, higher lignin content, and greater gene expression level and higher metabolite contents than shade susceptible one. So these characteristics could be used for screening the shade-tolerant soybean for intercropping.

Rejuvenating soybean(Glycine max L.)growth and development through slight shading stress

The impact of increased shading stress on agronomic traits,photosynthetic performance and antioxidants activities in leaves of two soybeans cultivars(D16 and E93)was studied.Soybean seedlings were grown in pots and exposed to no shade(S0),slight shade(S1),moderate shade(S2),and heavy shade(S3).Our findings showed that under the S3 in both cultivars,leaf fresh weight(LFW),specific leaf area(SLA)and leaf thickness decreased signifiantly,accompanied by a reduction in photochemical parameters including the maximum quantum yield(Fv/Fm)and electron transport rate(ETR).Furthermore,compared to SO,S1 significantly increased the ETR,sucrose content and the activity of catalase(CAT)in both D16 and E93 cultivars while S2 and S3 decreased the activity.However,under all treatments of shading stress,the antioxidant activities of superoxide dismutase(SOD)and peroxidase(POD)were lowered in both cultivars.Such morphological and physiological plasticity to adapt S1 compensates for the decrease in biomass and leads to seed weight compared to that obtained with an amount of normal light.Through configuring the space in the intercropping systems,S1 could be helpful for optimum growth and yield.Redesigning photosynthesis through S1 for the intercropping systems could be a smart approach.

Weak stem under shade reveals the lignin reduction behavior

Shades caused by neighboring tall plants in intercropping systems and weak sunlight are constraints in yield optimization. Shade influences many aspects of plant growth and development, leading to weak stems and susceptibility to lodging. The plant cell wall is composed of certain proteins that allow the walls to stretch out, a process called cell wall loosening. Shade affects anatomical, morphological, and physiological traits of plants, thus reducing the physical strength of the stem in crops by changing the loosening of cell walls. Flexibility of cells facilitates further modifications such as wall loosening. In addition, shade stress causes increased internode length, and reduced xylem synthesis and photosynthesis. In shaded plants, lignin deposition in vascular bundles and sclerenchyma cells of stems is decreased. Lignin is a light sensitive phenolic compound and shading decreases the transcript abundance of several phenolic compound(flavone and lignin) related genes. Shading significantly influences the metabolic activities of phenylalanine ammonia-lyase(PAL), peroxidase(POD), 4-coumarate: CoA ligase(4 CL), and cinnamyl alcohol dehydrogenase(CAD) involved in lignin biosynthesis. Furthermore, suppression of lignin biosynthesis activities by abiotic stresses causes abnormal phenotypes such as collapsed xylem, bent stems, and growth retardation. In this review, the underlying mechanisms illustrate that under shading conditions reduced lignin content results in slender, weak, and unstable stems. The objective of this review is to elaborate lignin biosynthesis and its variability under stressful environmental conditions, especially in shade stress environments. The effects of shade on stem lignin metabolism are discussed on the morphogenetic, physiological, and proteomic levels.

Exploration of Genetic Pattern of Phenological Traits in Wheat (Triticum aestivum L.) under Drought Stress

Drought is the major detrimental environmental factor for wheat(Triticum aestivum L.)production.The exploration of genetic patterns underlying drought tolerance is of great significance.Here we report the gene actions controlling the phenological traits using the line×tester model studying 27 crosses and 12 parents under normal irrigation and drought conditions.The results interpreted via multiple analysis(mean performance,correlations,principal component,genetic analysis,heterotic and heterobeltiotic potential)disclosed highly significant differences among germplasm.The phenological waxiness traits(glume,boom,and sheath)were strongly interlinked.Flag leaf area exhibits a positive association with peduncle and spike length under drought.The growing degree days(heat-units)greatly influence spikelets and grains per spike,however,the grain yield/plant was significantly reduced(17.44 g to 13.25 g)under drought.The principal components based on eigenvalue indicated significant PCs(first-seven)accounted for 79.9%and 73.9%of total variability under normal irrigation and drought,respectively.The investigated yield traits showed complex genetic behaviour.The genetic advance confronted a moderate to high heritability for spikelets/spike and grain yield/plant.The traits conditioned by dominant genetic effects in normal irrigation were inversely controlled by additive genetic effects under drought and vice versa.The magnitude of dominance effects for phenological and yield traits,i.e.,leaf twist,auricle hairiness,grain yield/plant,spikelets,and grains/spike suggests that selection by the pedigree method is appropriate for improving these traits under normal irrigation conditions and could serve as an indirect selection index for improving yield-oriented traits in wheat populations for drought tolerance.However,the phenotypic selection could be more than effective for traits conditioned by additive genetic effects under drought.We suggest five significant cross combinations based on heterotic and heterobeltiotic potential of wheat genotypes for improved yield and enhanced biological production of wheat in advanced generations under drought.