温度逆境锻炼对低温胁迫下番茄幼苗细胞膜脂质过氧化产物及抗氧化酶活性的影响

为了探索番茄植物交叉适应现象及其生理机制,以番茄品种东农704为材料,研究了低温和高温锻炼后番茄幼苗在2℃低温下叶片中丙二醛(MDA)和抗氧化酶活性的变化。结果显示,番茄幼苗经过适宜的低温和高温锻炼均可提高幼苗的抗冷性,并且高温锻炼在提高番茄幼苗抗冷性方面明显优于低温锻炼。2℃低温胁迫1d,未经锻炼幼苗与锻炼幼苗相比,其MDA含量明显升高,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性大幅度下降,即使在恢复生长2d后,MDA仍维持在较高的水平,SOD、POD和CAT活性水平也较低。番茄幼苗在低温和高温锻炼后、低温胁迫后和恢复2d后,MDA含量和酶保护系统变化各有异同。上述研究结果表明番茄植物具温度逆境交叉适应性,低温和高温锻炼诱导的番茄抗寒机制存在着差异性。     

温度变化对番茄幼苗抗寒性的影响

在低温（１５℃）,中温（２０℃）,高温（２５℃）条件下生长的番茄幼苗,定植前１５ｄ放置在相同的高温条件（２５℃）测定各处理不同时期幼苗叶片中脯氨酸,束缚水,自由水含量,以观察其抗寒性能的变化,结果表明,在低温下生长的番茄幼苗抗寒性较强,中温下生长的幼苗次之,高温下生长的幼苗抗寒性最差,但三种处理的幼苗放置在同样的高温下抗寒性迅速下降,尤其是低温下生长的幼苗下降幅度最大,到定植叶时不同温度处理幼苗的     

夜间低温对番茄幼苗吸收矿质元素的影响

以辽园多丽番茄幼苗为试材,模拟北方冬春季节日光温室的低温条件,设置夜间低温6℃处理,以正常夜间温度15℃为对照,测定番茄幼苗植株对N、P、K、Ca、Mg元素的吸收情况,为低温季节设施番茄栽培和施肥提供理论依据。测定结果表明,夜间低温抑制了番茄幼苗根系对N、P、K、Ca、Mg元素的吸收,番茄幼苗N素在叶片中含量最高,而P素在根系中含量最高;番茄幼苗根系对K素的吸收随着处理时间的延长,与对照相比差距逐渐缩小,到7d时基本持平;低温处理3 d后,根系中Ca、Mg含量开始增大,而叶片中Ca、Mg含量与对照相比呈明显下降趋势。     

临界生长温度锻炼对棉苗抗冷性的影响

研究了棉苗经过不同低温(12℃、14℃、16℃)锻炼7 d后,对较长时间(7 d)的低温(4℃)胁迫的耐受能力,并探讨了与其相关的可能机理.结果表明:经不同低温锻炼7 d后,所有棉花品种的幼苗脯氨酸含量都有不同程度的增加,其中12℃临界生长温度锻炼后增幅最明显;临界生长温度(12℃)下锻炼后的棉苗能耐受较长时间(7 d...     

储播条件对超甜玉米种子田间出苗率和幼苗整齐度的影响

5－10℃低温储藏能提高超甜玉米种子的田间出苗率和幼苗整齐度。进一步的播期试验表明：（1）超甜玉米在低温条件下比在较高温度下，其种子田间出苗率和幼苗整齐度有较大幅度下降，特别是未经包衣剂处理的种子；（2）同时用田间出苗率和幼苗整齐度来衡量超甜玉米种子迅速整齐出苗的潜能具有重要意义。     

乙酰水杨酸对夜间亚低温番茄幼苗抗寒性的影响

为了使番茄在北方设施栽培中能更好的适应早春夜间亚低温的环境,选用‘辽园多丽’（耐寒品系）和‘丽佳大粉’（冷敏品系）2个番茄品系幼苗为试验材料,当番茄幼苗长至两叶一心期喷施不同浓度的乙酰水杨酸(ASA),通过测定番茄叶片丙二醛含量,电导率值以及脯氨酸含量,探讨外源ASA在夜间亚低温9℃胁迫下对番茄幼苗的影响。结果表明：‘辽园多丽’番茄品系40 mg/L的外源ASA和‘丽佳大粉’番茄品系120 mg/L的外源ASA可用于番茄幼苗的夜间亚低温防御,对低温胁迫幼苗起保护作用。所以,在番茄幼苗两叶一心期喷施最佳浓度的ASA,可以减少夜间亚低温对番茄幼苗的伤害,从而提高番茄幼苗抵御低温的能力。     

番茄种子萌发的高温耐性诱导

番茄种子萌发的适宜温度为25～30℃;在15℃和35℃下萌发,种子的活力显著”降。通过轻度的温度胁迫处理,可大大提高番茄种子在高温下的萌发／生长能力;15℃和30℃分别是预处理的适宜低温和高温。番茄种子经低温预处理后在随后的高温中萌发其活力提高,说明种子对高温和低温胁迫具有文叉适应能力。     

低温胁迫对早春茬番茄生长和产量的影响

以‘冬美F1’、‘金山511’、‘美粉869’、‘冠粉8号’4个番茄品种为材料对象,探究低温胁迫对不同番茄品种幼苗生长及产量影响,评价不同番茄品种耐寒性差异。试验以20℃/4℃、20℃/6℃、20℃/8℃、20℃/15℃为处理,以日光温室自然环境25℃/18℃为对照,各处理同时进行6天试验,分别在低温胁迫前、胁迫6天及定植10天后进行调查取样,测定番茄的耐寒指数、壮苗指数,记录产量以及畸形果个数。结果表明,过度的低温胁迫(4、6℃)使得番茄出现冷害现象,番茄生长指标有一定程度降低;适当的低温胁迫(8、15℃)能够提高番茄的壮苗指数,增加植株干物质积累,且不同品种番茄存在差异;番茄产量和单果重不受苗期低温胁迫的影响,但较低温度的胁迫会影响花芽分化,从而使畸形果数量增加。4个番茄品种的耐寒性由强到弱表现为‘冬美F1’、‘金山511’、‘美粉869’、‘冠粉8号’。试验结果可为关中地区早春茬番茄品种种植提供理论依据。     

油菜素内酯诱导番茄幼苗抗冷效果的影响

试验采用油菜素内酯（BR）诱导二叶一心期和五叶一心期番茄幼苗,研究BR诱导后低温胁迫对番茄幼苗抗冷性相关生理指标的影响。在5℃～10℃低温胁迫条件下,不同浓度BR处理,可降低幼苗叶片细胞膜透性,减少叶片中丙二醛的含量,可溶性糖和脯氨酸的含量明显升高,同时增加了幼苗的根系活力,提高幼苗抗冷性。研究表明,低温条件下,五叶一心期对番茄幼苗喷施0.1mg/LBR,其冷害指数可比对照降低32.7%,电导率比对照降低58.4%,丙二醛含量最少,仅为25.5649nmol/g,溶性糖含量最高,达到137.27umol/g,脯氨酸含量最高,为542.3ug/g,同时幼苗的根系活力变化较平稳,变化幅度仅为20.9%。     

外源褪黑素对低温胁迫下马铃薯幼苗抗氧化系统的影响

为了探究不同浓度外源褪黑素对冷驯化后低温胁迫下马铃薯幼苗生长的影响,以云南主栽马铃薯品种合作88为材料,采用人工模拟低温胁迫(4℃14 d,-2℃12 h)的方法,研究了不同外源褪黑素浓度(50,100,150μmol/L)对低温胁迫下马铃薯幼苗生长及活性氧代谢系统的影响,以探讨外源MT缓解低温胁迫对马铃薯幼苗伤害的可...     

The freezing characteristics of wheat at ear emergence

Wheat is occasionally exposed to freezing temperatures during ear emergence and can suffer severe frost damage. Few studies have attempted to understand the characteristics of freezing and frost damage to wheat during late development stages.

It was clearly shown that wheat appears to have an inherent frost resistance to temperatures down to −5 °C but is extensively damaged below this temperature. Acclimation, whilst increasing the frost resistance of winter wheat in a vegetative state was incapable of increasing frost resistance of plants at ear emergence. It is proposed that the ability to upregulate frost resistance is lost once vernalisation requirement is fulfilled.

Culms and ears of wheat were able to escape frost damage at temperatures below −5 °C by supercooling even to as low as −15 °C and evidence collected by infrared thermography suggested that individual culms on a plant froze as independent units during freezing with little or no cross ice-nucleation strategies to protect wheat from frost damage in the field appear to revolve around avoiding ice nucleation.     

Soil Temperature and Planting Depth Effects on Tef Emergence

Tef [ Eragrostis tef (Zucc.) Trotter] is an annual C4 grass crop that originated in Ethiopia. It has potential as a grain crop in the Great Plains because of its tolerance to drought and high temperatures. In Ethiopia, tef seed is typically broadcast on the soil surface and lightly incorporated. Shallow planting depths are used because the seed is very small and emergence can be limited by soil crusting. If planting equipment is to be used, planting depth may be important for successful tef production. The objective of this study was to identify optimal depths and soil temperatures to aid in developing tef planting recommendations for the central Plains. Tef was planted at five depths (0, 0.6, 1.3, 2.5 and 5.0 cm) in pots filled with a silt loam soil, and pots were placed in growth chambers at four temperature regimes (day/night: 15/19 °C; 19/23 °C; 23/27 °C and 27/31 °C). No plants emerged from the 5.0-cm depth, so this depth was not included in the analysis. Emergence was greatest for planting depths of 0.6 and 1.3 cm and lower at 0 and 2.5 cm depths. Temperature did not affect final emergence, measured 21 days after planting (DAP), but did influence emergence rates during the first 9 DAP. Plant dry matter production increased as planting depth increased, but plant dry matter per pot was not different among planting depths greater than 0.9 cm, suggesting that compensation between plants across different plant densities began early in the plants' life cycles. Our results show that tef seed can emerge from depths between 0.6 and 1.3 cm and that soil temperatures below 19 °C can slow emergence but should not affect final stands.     

Using Digital Image Analysis to Describe Canopies of Winter Oilseed Rape (Brassica napus L.) during Vegetative Developmental Stages

In our experiment digital image processing is used to predict characteristics in a winter oilseed rape canopy. A large series of images was taken in 2002–2003 in close intervals from a measuring area of 1 m². These images were automatically evaluated by a self‐written computer program analysing the red/green/blue colour channels of each pixel. The number of determined green pixels was then related to the total pixel count of the image. Image evaluation helped to determine canopy structure by digital image analysis subjected to several applications, i.e. soil coverage, leaf area index (LAI), dynamics of plant number during vegetative developmental stages including entire winter season. Furthermore, number of plants per m² and position of each plant were determined by image analysis. Results show that all parameters are dynamic during the vegetative developmental stages (germination–beginning of flowering) mainly depending on temperature. During the vegetative developmental stages number of plants varied. Emergence lasted 30 days resulting in large differences in growth and development of individual plants. During winter number of plants decreased due to longer phases of frost. Plant growth indicated by dynamics of LAI alternated with phases of cessation due to low temperatures above zero or frost. Reductions in soil coverage and LAI clearly started at daily mean temperatures below 5 °C. After the analysis, differences in LAI as well as changes in number of plants during the early phase crop development can serve (i) as input parameters to growth models, (ii) to improve canopy reflectance measurements by separating spectral signatures of soil and canopy and (iii) to determine and explain heterogeneities within the canopy.     

田间密植诱导抽穗期玉米叶片衰老时的光合作用机制

为理解田间密植是否诱导抽穗期玉米叶片衰老以及衰老叶片的光合作用规律和机制,本研究以玉米"先玉335"为材料研究了抽穗期栽培密度对穗位叶和穗下第4叶的光环境、比叶重、氮素含量、叶绿素含量、气体交换以及叶绿素荧光诱导动力学的影响。结果表明,随着密度的增加玉米冠层内的光强大幅降低,尤其穗下第4叶;穗位叶和穗下第4叶的比叶重降低。同时,穗位叶和穗下第4叶的氮素含量和叶绿素含量均随栽培密度增加而下降。不同栽培密度下穗位叶荧光诱导动力学曲线(OJIP)未发生明显改变,而高密度下穗下第4叶OJIP的J和I相的相对荧光产量较低密度有提高趋势。高密度下,穗位叶和穗下第4叶叶片的光合速率、气孔导度和蒸腾速率均降低;不过,穗位叶胞间CO2浓度降低,穗下第4叶胞间CO2浓度增加。我们认为,田间密植条件下异质性光环境可以迅速诱导抽穗期玉米冠层下部叶片(如穗下第4叶)衰老;该过程中,光合作用的限制因素不是光能吸收和电子传递,而可能是碳同化。     

Some causes of poor fruit set in Jucunda strawberries

Summary A study was made of the possible causes of poor fruit set occurring in the strawberry variety Jucunda. In experiments in which plants were exposed to different constant temperatures from the beginning of flowering it was found that fruit set in Jucunda was normal at temperatures of 17°C and higher, but decreased rapidly at lower temperatures to a very low level at 10°C. In other experiments, in which in each case the temperature treatments were started a different number of days before the begining of flowering, fruit set was always lower than in the experiments mentioned above, but here too the unfavourable effect of lower temperatures was quite distinct. The experimental results indicate that poor fruit set is Jucunda results from inadequate pollen production and that it will occur if temperatures during the period of flowering are below 17°C, and possibly also if temperatures at some time before flowering are higher than the normal temperatures prevailing in the field during that period.Fruit set in the variety Juspa which originated from a cross between Jucunda and the American variety Sparkle, showed sensitivity to temperatures before and during flowering which was identical, if less pronounced, with that of Jucunda. Thus it was confirmed that poor fruit set in Jucunda can be passed on to its progeny. The results of these experiments indicate under which conditions selection against poor fruit set can be effectively carried out in progenies derived from Jucunda.     

Hydrogen peroxide reduces heat‐induced yield losses in cotton (Gossypium hirsutum L.) by protecting cellular membrane damage

We investigated the effect of various growth substances such as hydrogen peroxide, salicylic acid (SA), moringa leaf‐extract (MLE) and ascorbic acid (ASA) on leaf physiology and seed cotton yield (SCY) of heat‐stressed cotton. Cotton plants were exposed to elevated temperatures at three reproductive stages, either by staggering planting time in the field or by increasing growth cabinet temperatures (38/24°C and 45/30°C) in glasshouse. Elevated temperature at any reproductive phase significantly damaged cellular membrane and reduced SCY. Plants exposed to 38/24°C and 45/30°C in glasshouse produced 63% and 22% lower SCY, respectively, compared with plants under optimal temperature ((32/20°C). In response to high temperature, cotton plants up‐regulated activities of anti‐oxidative enzymes e.g. peroxidase and ascorbic acid. However, this defensive system could not protect cellular membrane of stressed plants from extreme temperature (38 and 45°C). In contrast, growth substances such as H2O2, ASA and MLE significantly increased anti‐oxidative enzymes activity to an extent, which reduced heat‐induced damage to cellular membrane. No significant effect of any regulator was observed on SCY under optimum temperatures; although H2O2, MLE and ASA significantly increased SCY of heat‐stressed cotton. Hydrogen peroxide increased SCY of April and May thermal regimes crops by 16% (averaged across both sowing dates) under field, while it caused 14% and 20% increase in SCY of plants exposed to sub (38/24°C) and supra optimal (45/30°C) thermal regimes under glasshouse. We concluded that growth regulators, specifically, H2O2 can protect cotton crops from heat‐induced cellular membrane damage by up‐regulating antioxidant defense system.     

Temperatures and the growth and development of wheat: a review

We start by outlining the general effects of climatic variability and temperature extremes on wheat yields in the context of extreme event effects on crop processes for climatic impacts studies. We then review literature describing the responses of wheat plants to extreme temperatures. Cardinal temperature thresholds for different phenological processes in wheat are identified and we outline the effects of temperature on rates of growth and development. Finally, we assess the implications of the above for future climatic impact studies.Our summary shows how relatively small and consistent are the standard errors of the cardinal mean temperatures for many of the processes examined. Cardinal temperatures are conservative between studies and are seemingly well-defined in wheat. Into this category we put the lethal limits for wheat, the sterility response at anthesis, the cardinal temperatures for vernalization and some of the base and optimal temperatures. Important questions for the future involve the effects of combinations of extreme events and the modelling of specific effects such as the influence of high temperatures on grain set.     

Fluorimetric Determination of the Genetic Variability Existing for Chilling Tolerance in Sweet Sorghum and Sudan Grass

Chilling temperatures drastically inhibited the photochemical quenching of chlorophyll fluorescence (q_Q) measured in intact leaves photosynthesizing under steady-state conditions. This effect appeared, however, to be characteristic of chilling-susceptible plant species and was not observed in plants which are known to be chilling-tolerant, indicating that the measurement of q_Q can serve in practice to estimate rapidly the relative chilling tolerance of crop plants. A large number (28) of sweet sorghum (Sorghum bicolor) and Sudan grass (Sorghum sudanense) genotypes were screened for chilling tolerance using this rapid q_Q method. Although sweet sorghum and sudan grass obviously behaved as chilling-sensitive plants, a considerable variation for chilling susceptibility was observed among the different genotypes tested. Some sweet sorghum varieties, such as ‘Dale’ and ‘Keller’, and most of the sudan grass varieties appeared to possess a certain degree of resistance towards low temperature stress, indicating the existence of useful germplasms in Sorghum for improving stress tolerance.     

Attempts at Avoiding the Yield Constraints of Bread Wheat (T. aestivum) in Mediterranean Environments

In bread wheat, in spite of the upward trend of grain yield, the Italian average production remains far below that of Central or Northern Europe. Recognized constraints are water availability to plants and the increase of air temperature during the grain filling period. To quantify these aspects, three varieties remarkably different in several morphophysiological traits were grown for three years under different water regimes in two locations of North and Central Italy.
The grain yield potential of the two locations was similar although if in the Southern location the plants were taller, with a denser canopy and a greater number of smaller seeds. Irrigation after flowering increased yield and yield stability; however, at high air temperatures, dry matter accumulation ceased even though water in the soil was abundantly available. These results suggest the possibility of applying irrigation during grain filling, but a more realistic approach seems to be selection of new varieties characterized by moderate carliness and capacity to sustain kernel growth for a longer period even in the presence of high air temperatures.