The Temperature Response of Gas Exchange in Sorghum Leaves and the Effect of Heterosis

The aim of this research was to describe the temperature responseof gas exchange in grain sorghum (Sorghum bicolor L. Moench)leaves as temperature was increased in a fashion similar toits daily increase in a hot environment. The hypothesis thatsorghum hybrids manifested heterosis for carbon dioxide exchangerate on a wider temperature range as compared with their parentallines was also evaluated. Gas exchange of detached turgid leaveswas measured in four sorghum hybrids and their parents as leaftemperature rose steadily from 32 °C to 43 °C in 4 h.CER was maximal at about 37–40 °C depending on thegenotype. In one genotype (Tx378), CER was maximal at 42 °C.In three out of four hybrids significant heterosis was foundfor CER at the lower, the higher or at the full range of temperaturestested depending on the hybrid. Consequently, all three heterotichybrids displayed a greater temperature range for high CER ascompared with their parents. Heterosis in CER was largely explainedby heterosis in stomatal conductance, though the effects ofnon-stomatal components could not be elucidated here. Heterosisin transpiration was revealed in the same three hybrids, especiallyat moderate temperatures. Since heterosis in CER was relativelygreater than heterosis in transpiration, significant heterosisin transpiration ratio at moderate temperatures was seen intwo of the four hybrids. An effect of heat hardening on CERwas observed in parental line Tx430 and its two hybrids as seenin the reduction of CER at 36–37 °C and its subsequentrecovery as temperatures rose slowly to 43 °C. The effectof heat hardening on photosynthesis was also observed in someof the genotypes as a hysteresis in the association betweenstomatal conductance and CER as temperatures increased. Thishysteresis indicated that, for the same stomatal conductance,CER was greater after than before leaves were exposed to hightemperature. Key words: Photosynthesis, hybrid vigour, heat stress     

多效唑对高粱生长发育及生理的影响

为了解喷施多效唑对高粱(Sorghum bicolor)生长发育和生理的影响,在高粱品种'农大红1号'拔节期喷施多效唑水溶液,对高粱的生长发育和生理指标进行了研究.结果表明,喷施不同浓度的多效唑后,高粱株高均比对照降低,基部节间长度缩短,茎粗增加,且穗粒重也提高.同时,高粱叶片的叶绿素含量和净光合速率提高,且抗氧化酶活...     

松土对干旱胁迫下油橄榄抗性生理及土壤环境因子的影响

以田间树龄6~7年的油橄榄树为对象,设置充分灌溉(W_(CK))、2/3灌溉量(W_1)、1/3灌溉量(W_2)3个土壤水分环境条件,考察松土对干旱胁迫下油橄榄根际土壤理化指标、土壤酶活性、油橄榄叶片抗性生理及根系活力的影响,探究松土提高油橄榄抗旱性的生理机制,为油橄榄的抗旱生产提供理论和技术支持。结果表明:(1)随着灌溉量的减少,油橄榄叶片O~-·_2产生速率、MDA含量和H_2O_2含量都有所增加,油橄榄叶片受到了干旱造成的氧化胁迫,但松土处理均抑制了O~-·_2产生速率、MDA含量和H_2O_2含量的增长,同时也缓解了细胞膜稳定指数的下降;(2)经松土处理后,除SOD活性和还原型谷胱甘肽含量增加不明显外,油橄榄叶片POD活性、CAT活性均比不松土处理显著增加,增强了其抵御氧化胁迫的能力;(3)松土处理使油橄榄根际土壤相关酶活性、根际土壤含水量有所增加,但土壤pH值有所降低,这些根际土壤环境因子的变化对于油橄榄的矿质营养和水分状况的改善都具有积极的作用,尤其在因灌溉不足引起干旱胁迫的情形下更为重要。(4)松土处理提高了油橄榄叶片叶绿素含量和根系活力。研究认为,松土处理通过改善干旱胁迫下油橄榄的根际微环境条件,强化油橄榄叶片的酶促和非酶促抗氧化系统活性,提高自身渗透调节能力,增强根系活力,从而有效提高油橄榄对干旱的整体抗性。     

Prion Switching in Response to Environmental Stress

Evolution depends on the manner in which genetic variation is translated into new phenotypes. There has been much debate about whether organisms might have specific mechanisms for “evolvability,” which would generate heritable phenotypic variation with adaptive value and could act to enhance the rate of evolution. Capacitor systems, which allow the accumulation of cryptic genetic variation and release it under stressful conditions, might provide such a mechanism. In yeast, the prion [PSI⁺] exposes a large array of previously hidden genetic variation, and the phenotypes it thereby produces are advantageous roughly 25% of the time. The notion that [PSI⁺] is a mechanism for evolvability would be strengthened if the frequency of its appearance increased with stress. That is, a system that mediates even the haphazard appearance of new phenotypes, which have a reasonable chance of adaptive value would be beneficial if it were deployed at times when the organism is not well adapted to its environment. In an unbiased, high-throughput, genome-wide screen for factors that modify the frequency of [PSI⁺] induction, signal transducers and stress response genes were particularly prominent. Furthermore, prion induction increased by as much as 60-fold when cells were exposed to various stressful conditions, such as oxidative stress (H₂O₂) or high salt concentrations. The severity of stress and the frequency of [PSI⁺] induction were highly correlated. These findings support the hypothesis that [PSI⁺] is a mechanism to increase survival in fluctuating environments and might function as a capacitor to promote evolvability.     

高粱幼苗水分胁迫诱导表达差异cDNA的研究

以高粱为试验材料,用-0．7MPa的PEG-6000高渗溶液对其幼苗进行水分胁迫处理,利用mRNA差异显示技术分离得到53条高粱水分胁迫诱导表达的cDNA片段,其中包括5个完全诱导表达片段,43个上调片段和5个下调表达片段。经过Reverse Northern验证,筛选出13个差异表达的cDNA片段,并进行克隆测序。经GenBank查询,10个片段序列与已知序列有较高的同源性,3个片段同源性非常低,可能为新基因。     

Carbon Balance of Sorghum Plants during Osmotic Adjustment to Water Stress

The daily (24-hour) carbon balances of whole sorghum plants (Sorghum bicolor L. Moench cv BTX616) were continuously measured throughout 15 days of water stress, followed by rewatering and 4 more days of measurements. The plants were grown under controlled environment conditions typical of warm, humid, sunny days. During the first 12 days, osmotic potentials decreased in parallel with decreased water potentials to maintain pressure potentials near 0.5 kilojoules per kilogram (5 bars). Immediately before rewatering on day 15, the water potential was −3.0 kilojoules per kilogram. Osmotic adjustment at this point was 1.0 kilojoules per kilogram, as measured by the decrease in the water potential at zero turgor from its initial value of −1.4 kilojoules per kilogram.

Gross input of carbon was less but the fraction retained was greater because a smaller fraction was lost through respiration in stressed plants than in unstressed plants. This was attributed to a lower rate of biomass synthesis, and conversely a higher rate of storage of photosynthate, due to inhibition of leaf expansion. The reduction in the cost associated with biomass synthesis more than balanced any metabolic cost of osmotic adjustment. The net daily gain of carbon was always positive in the stressed plants.

There was a large burst of respiration on rewatering, due to renewed synthesis of biomass from stored photosynthate. Over the next 3 days, osmotic adjustment was lost and the daily carbon balance returned to that typical of nonstressed plants. Thus, osmotic adjustment allowed the stressed plants to accumulate biomass carbon throughout the cycle, with little additional metabolic cost. Carbon stored during stress was immediately available for biomass synthesis on rewatering.

     

The Location of Muscle Calcium with Respect to the Myofibrils

Autoradiographs have been prepared from frog toe muscles soaked in Ca⁴⁵ and fixed with an osmium-oxalate solution. A majority of the grains over the A bands were over the myofibrils. The grain density over the I bands was greatest over the space between the myofibrils. The significance of this distribution is discussed in the light of previous information about the longitudinal distribution of Ca⁴⁵ in skeletal muscle.     

慈姑（Sagittaria sagittifolia L.）对环境镉胁迫因子的应答

主要研究了水环境中Cd2+污染对慈姑(Sagittaria sagittifolia L.)根的毒害影响.结果表明:在Cd2+胁迫下,慈姑根出现不同程度的褐变、发黑,生长受到限制;叶和根尖细胞超微结构受损,叶绿体膨大、类囊体排列紊乱、线粒体嵴减少、空泡化、染色质凝集等;根尖细胞在扫描电镜下呈细胞壁增厚、细胞形状扭曲和排列不规则现象.能谱分析结果表明随外界Cd2+浓度增大,单个慈姑根尖中的Cd2+含量升高,其他营养元素的吸收受到不同程度的影响.Cd2+对慈姑的毒害有明显的剂量效应和时间效应.     

植物弱光逆境生理研究综述

弱光是目前影响设施生产的重要不利环境因素之一。本文综述了弱光对植物生长发育 和光合特性的影响及其信号转导途径,并在此基础上讨论了植物对弱光的适应途径和今后植 物弱光逆境生理的研究方向。     

环境胁迫下植物MAPK多叠级联响应(英文)

Plant mitogen-activated protein kinases(MAPKs) are involved in growth,evelopment and responses to endogenous and environmental cues．which link stimuli that areactivated by external sensors to cellular responses．In Arabidopsis,as amodel,all of MAP kinase genes have been listed and classified．Based on the Arabidopsis MAPK families．a number of MAPk inase genes in other plant species have been recently isolated and classified．Most of the cloned MAPk inase genes can be activated by avariety of stresss timuli including pathogen infection．wounding．temperature,drought．salinity．osmolarity．UV irradiation．ozone and reactive oxygen species．Some tools and strategies are used to investigate their functions and signal pathways under different environmental stresses．indicating complexity and crosstalk of plant MAPk inase signaling pathways．It is still necessary to explore more novel tools and strategies to clarify MAPK signaling pathways,and how to apply the MAPK cascade to improve the resistance of crop to abiotic and biotic stress     

植物弱光逆境生理研究综述

弱光是目前影响设施生产的重要不利环境因素之一。本文综述了弱光对植物生长发育和光合特性的影响及其信号转导途径,并在此基础上讨论了植物对弱光的适应途径和今后植物弱光逆境生理的研究方向。     

不同水分胁迫对刺槐生理的影响

本文以二年生刺槐为供试材料,探讨水分胁迫对其生理的影响,为园林绿地中刺槐的灌溉提供理论指导.结果表明,水淹和干旱胁迫明显影响刺槐的生长.水淹11 d后,qP值、ETR值、Fv'/Fm'值和净光合速率的明显下降,qN值上升,19 d后植株死亡.中度干旱胁迫(土壤含水量在8%～15%之间)对植株生长有一定影响,表现为净光合速率的下降和qN值上升等;干旱胁迫(土壤含水量低于10%)严重抑制植株的生长,表现为qN值上升,而qP、ETR、Fv'/Fm'和净光合速率下降,处理19 d后干旱组植株死亡.轻度干旱(土壤含水量在15%～25%之间)适宜植物生长,表现为3次测定的qP、ETR、Fv'/Fm'、Fv/Fm和净光合速率都较高且稳定.土壤含水量日变化在15%～25%以内受轻度干旱胁迫是园林中刺槐的最佳灌溉方式,既不影响景观效果,同时也能节约灌溉用水.