荒漠植物白刺对模拟增雨的光合响应机制

【目的】研究不同增雨条件下白刺叶片的光合作用和叶绿素荧光特性,从光合生理角度探讨白刺对增雨的响应机制。【方法】以乌兰布和沙漠东缘地区典型荒漠植物白刺为研究对象,设置不同的增雨梯度(增加年均降水量的0,25%,50%,75%和100%),对自然生长的白刺沙包进行人工模拟增雨,利用 Li－6400xt便携式光合测定系统分析仪(USA,LI-COR)测定不同增雨条件下白刺叶片净光合速率(Pn)日动态变化、光响应曲线、CO2响应曲线以及叶绿素荧光参数,并根据 Pn 日变化曲线和响应曲线计算叶片日光合总量(∑Pn )以及各光合生理参数。【结果】1)75%和100%增雨对日均 Pn 和∑Pn 影响显著,日均 Pn 比 CK分别高32.74%和37.64%,∑Pn 比 CK 分别高32.01%和38.43%,说明增雨使白刺光合能力增强,日光合产物的积累增加。2)增雨使白刺表观量子效率( AQY)和光饱和点( LSP)升高,25%,50%,75%和100%增雨的 AQY 比 CK 分别高17.24%,31.03%,37.93%和24.14%,LSP比 CK分别高14.6%,6.0%,3.0%,26.1%,说明白刺叶片利用弱光的能力增强,对强光的利用范围增加,光能转化效率提高,有利于光合作用的高效进行。3)随着增雨量的增加,羧化效率(CE)呈现出逐渐增加的趋势,其中,100%增雨的 CE比 CK高5.73%;增雨使 CO2饱和点( CSP)升高,50%,75%和100%增雨的 CSP 显著高于 CK,分别比 CK高23.67%,28.35%和29.13%,说明白刺叶片 RuBP羧化酶和光合碳循环酶的活性增强,对高CO2浓度的利用范围增加。4)增雨使白刺叶片的原初光化学量子效率( Fv/Fm )、实际光化学量子效率(ФPSⅡ)、电子传递速率( ETR)和光化学猝灭系数( qP )提高,说明增雨有利于白刺叶片PSⅡ反应中心活性增强、开放比例提高,有利于叶片把所捕获的光能转化为生物化学能,并将更多的光能用于推动光合电子传递。【结论】白刺能够调节光合机构的功能、改变自身生理特性、增强对环境资源的利用能力来适应增雨的变化。     

5个油茶优良无性系光合及叶片解剖特征比较分析

为给进一步筛选高光效、优良的油茶无性系提供参考依据,选择5个油茶优良无性系(‘湘林’系列XL210、XL82、XL190、XL81、XL14)9年生植株,于2013年7月观测了其光合参数及叶片解剖特征。结果表明:净光合速率(Pn)的日变化曲线,XL14呈"单峰型",其他无性系均为"双峰型",不同无性系峰值出现的时间及峰值大小不完全相同,各无性系的Pn日均值从大到小依次为XL14XL81XL82XL210XL190,各无性系的单位面积产油量均值都随Pn值的增大而增大,Pn与叶绿素a、叶绿素(a+b)和叶绿素a/b之间均存在显著的正相关关系;5个无性系的叶片解剖特征值之间差异明显,栅栏组织/叶片厚度、栅栏组织/海绵组织的比值与Pn及单位面积产油量间均呈显著正相关。     

Mechanisms associated with tiller suppression under stagnant flooding in rice

Stagnant flooding (SF) during vegetative growth triggers stem elongation usually at the cost of tiller production in rice, reducing grain yield. To explore physiological mechanisms associated with tillering suppression under SF, three contrasting genotypes (Swarna and Swarna‐Sub1, both sensitive and IRRI154, tolerant) were evaluated under standing water depths of 0, 5, 30 and 50 cm. SF significantly suppressed tiller formation but increased plant height, root biomass, shoot elongation (ratio of plant height before and after flooding), leaf emergency and non‐structural carbohydrate (NSC) concentration (in root–shoot junction) in all genotypes at the early stage of development. Chlorophyll concentration in the upper leaves (upper most fully expanded leaf at top) was higher than in lower leaves (lowest green leaf at base), but decreased under SF in both. SF increased hydrogen peroxide (H₂O₂) at the early stage of treatment, with concomitant increase in malondialdehyde (MDA) production by stems and leaves. MDA concentration in root–shoot junction increased but delayed. Tiller number correlated negatively with plant height, shoot elongation, leaf emergency, MDA concentration in leaves and root–shoot junction, root biomass, and NSC concentration in the root–shoot junction. The results suggested existence of compensatory mechanisms between tiller growth and shoot elongation in rice for resilience under SF, where energy is mainly diverted for shoot elongation to escape flooding. The SF‐tolerant genotype produced less H₂O₂ and maintained energy balance for higher survival and better growth under stagnant flooding.     

Potassium deficiency impedes elevated carbon dioxide‐induced biomass enhancement in well watered or drought‐stressed bread wheat

Potassium (K) deficiency reduces photosynthesis and biomass production of crop plants and also renders them vulnerable to drought stress, whereas elevated carbon dioxide (CO₂) has a positive effect on photosynthesis and yield and ameliorates the adverse effects of drought stress. This study aimed to characterize the physiological responses of wheat (Triticum aestivum L.) stressed with K deficiency under elevated CO₂ and drought conditions. Increased biomass production caused by elevated CO₂ as a consequence of increased photosynthesis and water use efficiency was absent in young K‐deficient wheat plants. Shoot K concentration was negatively affected by elevated CO₂ particularly under K‐deficient conditions, whereas K content per plant was greatest in plants supplied with adequate K and adequate water. Specific leaf weight was increased as a consequence of carbohydrate accumulation in the source leaves of K‐deficient plants particularly under elevated CO₂ and drought stress. Potassium deficiency clearly impeded the impact of elevated CO₂ in both well watered as well as drought‐stressed plants. Adequate K fertilization is a prerequisite for efficient harvesting of atmospheric CO₂ through increased photosynthesis, decreased transpiration, and increased biomass production under changing atmospheric CO₂ and soil moisture conditions.     

Effects of 5‐aminolevulinic acid on water uptake,ionic toxicity,and antioxidant capacity of Swiss chard (Beta vulgaris L.) under sodic‐alkaline conditions

Sodic‐alkalinity may be more deleterious to plant growth than salinity. The objectives of this study were to determine whether 5‐aminolevulinic acid (ALA: an essential precursor for chlorophyll biosynthesis) foliar application could improve the sodic‐alkaline resistance of Swiss chard (Beta vulgaris L. subsp. cicla ) by regulating water uptake, ionic homeostasis, photosynthetic capacity, and antioxidant metabolism. Eight‐week‐old uniform plants were grown in nutrient medium without and with a sodic‐alkaline regime generated by a mixture of NaHCO₃ and Na₂CO₃ (NaHCO₃ : Na₂CO₃ = 9:1 molar ratio) for 12 d, and leaves were sprayed daily with water or ALA. The Na⁺ and ALA concentrations were gradually increased to 60 mM and 120 μM, respectively. ALA foliar application alleviated the physiological damage from sodic‐alkalinity, as reflected by the increases in plant dry weight, relative growth rate, chlorophyll, Mg²⁺ concentration, and the decrease in Na⁺ concentration. However, ALA foliar application did not change the water uptake capacity or the concentration of K⁺, Fe³⁺, and endogenous ALA in leaf tissues under sodic‐alkaline conditions. ALA foliar application effectively mitigated damage from sodic‐alkalinity because of the increased activity of antioxidant enzymes (catalase and guaiacol peroxidase), particularly superoxide dismutase activity, which was maintained at the same level as for control plants. These results suggest that ALA foliar application alleviated sodic‐alkaline stress mainly owing to its antioxidant capacity, and superoxide dismutase has the main responsibility for reducing oxidative stress in Swiss chard.     

基于计算机视觉技术的玉米叶绿素含量检测研究

植株叶片中叶绿素浓度的高低与植株进行的光合作用效率、植株的整体生长状况息息相关,在农业生产过程中,常常根据叶片中叶绿素含量(SPAD)的多少来精确的判断植物的生长状态,也是控制植株长势的依据。传统的叶绿素含量检测方式分光光度法,存在耗时长、步骤多、操作要求高等问题,而采用计算机视觉技术处理图像的过程更加准确、高效,不会像人眼分析时受到主观因素的影响导致偏差。为此,基于计算机视觉技术来检测玉米叶片中叶绿素含量,利用扫描仪采集玉米叶片的图像,将图像输送至计算机,然后通过软件处理图像,分割出图像中有效像素的颜色特征值,将特征值转换就可以得到玉米叶片中叶绿素。试验结果显示:利用计算机视觉技术可以准确地测定玉米叶片中叶绿素含量,进而进行合理施肥,避免浪费,对增加玉米的产量具有极大的价值。     

Postharvest UV-C treatment combined with 1-methylcyclopropene (1-MCP), followed by storage in continuous low-level ethylene atmosphere,improves the quality of tomatoes

Mature green tomatoes (Solanum lycopersicum L. cv Neang Pich) were exposed to 13.6 kJ m^?2 UV-C or 0.5 μL L^?1 1-MCP or combination of 13.6 kJ m^?2 UV-C and 0.5 μL L^?1 1-MCP, with appropriate untreated controls. After treatment, tomatoes were stored in air containing 0.1 μL L^?1 ethylene at 20°C and 100% RH. The untreated fruit ripened significantly faster than those of all other treatments. UV-C treatment alone was able to delay fruit ripening by up to 5 days longer compared to untreated fruits whilst the additional of 1-MCP further delayed fruit ripening. UV-C and 1-MCP treatments alone or in combination had significantly slower ethylene production rates throughout the storage period. The fruit treated with the combination of 1-MCP and UV-C was significantly firmer and had higher total phenolic content compared to that of the other treatments. However, there was no difference between treatments in soluble solids content/titratable acids ratio, chlorophyll content, lycopene content and total antioxidant activity. These results show that UV-C and 1-MCP treatment delay ripening and improve the quality of tomatoes in the presence of low-level ethylene during storage. This new treatment could be used to extend the shelf-life of mature green tomatoes through the supply chain without the use of refrigeration.     

覆盖对烟田土壤酶活性及烤烟叶片荧光特性的影响

通过对烤烟大田3种不同覆盖方式的覆盖效应比较表明:覆盖明显增强了土壤过氧化氢酶和蔗糖酶活性,对脲酶活性有一定抑制作用;在烤烟生长前期,液膜覆盖处理土壤过氧化氢酶活性较对照和地膜覆盖处理分别平均提高5.72%、23.19%,且覆盖处理间差异达0.05显著水平;覆盖处理的蔗糖酶较对照平均提高0.8%,但3个处理间差异均不显...     

考虑植株氮垂直分布的夏玉米营养诊断敏感位点筛选

探明夏玉米氮素营养生化指标(叶绿素a、叶绿素b、类胡萝卜素、叶片氮含量和叶片氮积累量)与叶片SPAD值垂直分布特征及两者间定量回归关系,确立基于叶绿素仪的夏玉米氮营养无损诊断敏感叶位和叶片部位,以实现氮营养时空变化的快捷和精准监测。利用2018-2019年连续2季不同氮营养水平下夏玉米关键生育期主茎各叶位(顶1叶~顶12叶,TL1~TL12)和叶片部位(每张叶片从叶片基部开始根据叶片长度每20%分为1个测试区间) SPAD值及氮营养指标数据,研究基于偏最小二乘(partial least square, PLS)回归模型的夏玉米不同位点SPAD值与氮营养指标间关系,确定可稳定指示夏玉米氮营养空间异质性变化的敏感叶位及叶片部位。结果表明,不同叶位间夏玉米叶片SPAD值和氮营养指标于植株间分布均呈典型的"钟型"特征,至TL5或TL6时达至峰值。同一叶位不同部位间SPAD值由20%至100%位点时则逐步升高,且80%~100%位点间无显著差异(P>0.05)。PLS分析结果显示,夏玉米不同叶位SPAD值与氮营养指标间模型精度决定系数(coefficient of determination, R2)和相对分析误差(relative percent deviation,RPD)范围分别为0.693~0.821和1.425~2.744。不同测试位点R2和RPD值范围则分别为0.660~0.847和1.607~2.451,满足模型精确诊断需求。此后,基于PLS模型中各叶位和叶片部位无量纲评价指标变量重要性投影值(variable importance for projection,VIP),确定顶4叶(TL4)完展叶60%~80%区间为夏玉米氮营养诊断的敏感区域,VIP值均高于临界值1.40,预测效果较为理想。研究可为实现氮营养的高效、快捷诊断和精准施氮提供参考。     

基于无人机多光谱遥感的冬小麦叶绿素含量反演及监测

旨在实现冬小麦各生育期叶绿素含量的准确估测,探究其时空变化规律。利用无人机获取冬小麦越冬期、返青期、拔节期、孕穗期和灌浆期的高分辨率多光谱图像,同时采集地面SPAD数据。选取三类光谱参数建立反演模型,优选出各生育期的最佳预测模型,并定量监测试验区冬小麦叶绿素含量时间变化和空间分布。结果表明：原始波段模型和波段倒数对数模型分别为越冬期及其他生育期叶绿素含量预测的最佳模型,拟合精度R²>0.59;时空分布上,灌浆期前试验区冬小麦叶绿素含量呈南北高、中部低特点,灌浆期则呈北高南低的趋势,叶绿素含量从越冬期到拔节期逐步增加,拔节期到孕穗期开始降低,孕穗期到灌浆期则大幅度降低。本研究建立的倒数对数预测模型,精度较高,且适用于返青到灌浆的4个生育期,对于试验区冬小麦叶绿素含量有较好的时空监测效果。