干旱缺钾对油菜内源激素、光合作用和叶绿素荧光特性的影响

为了解钾肥对抗旱的生理影响,以抗旱性不同的两个油菜品种川油36（敏感）和油研57（耐旱）为材料,采用水培试验,调查干旱缺钾对油菜内源激素、光合作用和叶绿素荧光特性的影响。设置缺钾（0.01 mmol/L K₂SO₄）和正常钾肥（1.0 mmol/L K₂SO₄）两个梯度,加入7%的PEG6000模拟干旱,分别记为LK和NK处理。结果发现,干旱胁迫严重抑制油菜生长,不同钾肥水平对油菜生长和激素水平影响显著,与NK处理相比,LK处理下油菜生物量和叶片吲哚乙酸（IAA）、细胞分裂素（CTK）和油菜素内酯（BR）含量显著降低,而脱落酸（ABA）含量显著增加。干旱胁迫下钾肥水平对油菜光合作用影响显著,与NK相比,LK处理下油菜净光合速率、气孔导度、核酮糖-1,5-二磷酸羧化酶（RuBP羧化酶）活性、磷酸烯醇式丙酮酸羧化酶（PEPC）活性均显著降低。干旱胁迫下光系统I（PSI）P700最大变化（Pm）和光下P700最大变化（Pm'）显著降低,LK处理下Pm'显著低于NK处理,而PSI受体侧限制非光化学量子产量[Y(NA)]显著高于NK处理。干旱胁迫导致光系统II（PSII）最大光化学量子产量（Fv/Fm）显著降低,与NK处理相比,LK处理下Fv/Fm和PSII调节性能量耗散[Y(NPQ)]显著降低,然而非调节性能量耗散[Y(NO)]显著增加。LK处理下抗旱品种油研57叶片IAA含量、CTK含量、叶绿素含量、净光合速率和Fv/Fm显著高于川油36,表现出更高的生物量。综上,干旱缺钾会诱导ABA积累,抑制生长促进类激素IAA、CTK和BR的合成,抑制油菜生长。干旱缺钾条件下,RuBP羧化酶和PEPC酶活性显著降低,同时PSI受体侧过度还原,PSII调节性能量耗散减弱,非调节性能量耗散量子产量增加,造成PSI和PSII活性下降,导致油菜光合作用降低并限制油菜生长。     

Tuber yield and tuber quality of several potato cultivars as affected by seasonal high temperatures and by water deficit in a semi-arid environment

Summary The effects of high temperatures and water deficit on potatoes were investigated under field conditions. Nine cultivars and one un-named seedling were grown in the spring and in the summer under high temperatures. In both seasons the cultivars were grown under 3 water regimes: adequate water supply, moderate water deficit, and severe water deficit that were achieved by a modification of the single line source sprinkler irrigation system. Severe drought reduced tuber yields in both seasons. Moderate tolerance to a moderate water deficit in the spring season was exhibited by Draga, Désirée, and Monalisa. Late and intermediate cultivars produced high tuber yields in the spring season, and early cultivars had relatively smaller yield losses in the summer. The extent of tuber disorders, sprouting, rotting and malformation, varied considerably. High temperatures enhanced sprouting, rotting and malformation and drought may enhance sprouting and malformation. This investigation was supported by a grant from the Ministry of Foreign Affairs, Technical Assistance Department, Netherlands.     

Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). I. Plant water status and the kinetics of chlorophyll fluorescence

Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F _o andF _v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F _v/(F _o+F _v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q_1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF _v/(F _o+F _v),M andq _1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.     

Assessment of the non-freezing cold sensitivity of wild and cultivated potato genotypes by chlorophyll fluorescence analysis

Summary Relative cold tolerances were determined for 18 genotypes of wild and cultivated potato (Solanum spp.); eleven were from high altitude and were considered to be adapted to cold environments, and the remaining seven were cultivars ofS. tuberosum of which four originated from Chile. Relative cold sensitivity of the genotypes was measured by the decrease in the rate of the induced rise in chlorophyll fluorescence in leaflets kept at 0°C in the dark. Most wild species showed a greater tolerance to the low temperature and the results show a large genotypic range within theSolanum spp. for cold tolerance at 0°C. genotypes ofS. tuberosum showed a large range in cold sensitivity. This genotypic range in cold sensitivity, the use of chlorophyll fluorescence analysis as a screening technique and the relationship betweenF _R andF _var are discussed.

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Zusammenfassung Für 18 Genotypen wilder und kultivierter Kartoffeln (Solanum spp.) wurden die K?ltetoleranzen ermittelt. Elf der Genotypen waren Wildspezies und galten als adaptiert an kalte Umgebungen. Die restlichen sieben waren Sorten vonS. tuberosum, von denen vier aus Chile stammten. Die relative K?ltesensibilit?t der Genotypen wurde anhand des Rückgangs des Ausmasses des induzierten Anstieg der Chlorophyll-Fluoreszenz in Bl?ttchen bei 0°C im Dunkeln gemessen, und wurde in Form der Zeit für einen 50 %igen Rückgang derF _R (maximale Rate des induzierten Anstiegs der Chlorophyll-Fluoreszenz) im Vergleich zur Kontrolle registriert. Die Mehrzahl der wilden Spezies zeigte eine h?here Toleranz für niedrige Temperatur, und die Ergebnisse zeigen eine grosse genotypische Schwankungsbreite für K?ltetoleranz bei 0°C innerhalb derSolanum-Spezies.S. albicans zeigte die gr?sste Toleranz gegenüber Stress mit einem K?ltetoleranz-Wert von 78 Stunden,S. tuberosum (CPC 3294) nur einem Wert von 24 Stunden für einen 50%igen Rückgang derF _R. Eine grosse genotypische Bandbreite scheint innerhalb vonS. tuberosum zu bestehen (Tabelle 1), welche sich als sehr wichtig für die Züchtung k?ltetoleranterer Sorten erweisen k?nnte. Gegenüber europ?ischen Sorten zeigten die chilenischen die gr?ssere Toleranz für niedrige Temperatur. Dennoch erwies sich die Sorte Moira k?ltetoleranter als andere europ?ische Sorten. Die in dieser Studie verwendete Chlorophyll-Fluoreszenz-Methode ist ein Schnelltest mit Anwendung von einzelnen Bl?ttchen, und, wie alle Kurzzeittests dieser Art, erfordert er Sorgfalt bei der Anwendung und bei der Ausdehnung der Ergebnisse auf die Pflanze als Ganzes und zum jeweiligen Wachstumsstadium über die Vegetationsperiode. Dennoch erweist sich die M?glichkeit, anhand der Chlorophyll-Fluoreszenz-Analyse sowohl inter-als auch intraspezifisch Abstufungen in der K?ltetoleranz zu unterscheiden, bei wilden und kultivierten Kartoffelspezies als potentieller Anwendungsbereich für die Methode, in zukünftigen Kartoffelzüchtungs-Programmen auf K?ltetoleranz zu selektieren.

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Résumé La tolérance relative au froid de 18 génotypes d'espèces sauvages et cultivées deSolanum a été déterminée. Onze étaient des espèces sauvages considérées comme adaptées à des conditions d'environnement froides et sept étaient des variétés deS. tuberosum, parmi lesquelles quatre originaires du Chili. Comparativement à des témoins non traités la relative sensibilité au froid étai évaluée par la perte d'intensité de fluorescence de la chlorophylle provenant de folioles conservées à 0°C dans l'obscurité. La majorité des espèces sauvages se montrait plus tolérante vis à vis des basses températures; dans l'ensemble les résultats mettaient en évidence une large gamme de tolérance à 0°C pour les espèces deSolanum: S. albicans était le plus tolérant au stress avec un temps de 78 heures alors queS. tuberosum (CPC 3294) y était le moins avec seulement 24 heures pour obtenir une extinction de la fluorescence de 50%. La gamme de tolérances rencontrée chezS. tuberosum (tableau 1) pourrait s'avérer très importante pour une hybridation ayant comme objectif l'obtention des variétés plus résistantes au froid. Les variétés chiliennes montraient une plus grande tolérance aux basses températures que les variétés européennes cependant, parmi ces derniéres, ‘Moira’ était plus tolérante au froid que les autres. La méthode d'évaluation basée sur la fluorescence de la chlorphylle utilisée dans cette étude est un test rapide n'utilisant que quelques folioles et, comme pour tous les tens simples et rapides, il est nécessaire d'être prudent avant de transposer les résultats obtenus à la plante entière et à toutes les époques de la période de croissance de la plante. Cependant la capacité de cette méthode à déceiler des degrés de tolérance au froid entre espèces sauvages et entre celles-ci et les variétés cultivées suggère un usage possible pour la détection de ce caractère dans les futurs programmes d'hybridation de la pomme de terre.

     

干旱及复水对油菜苗期光合及叶绿素荧光特性的影响

以西藏当地推广的油菜代表品种芥菜型油菜(Brassica juncea L.)年河1号、白菜型油菜（Brasscia rapa L.）青油17号和甘蓝型油菜（Brasscia napus L.)藏油5号为材料,设置持续干旱1周和2周的2个干旱处理及干旱后复水1周、2周、3周的3个时期,研究苗期干旱及复水对油菜光合及荧光特性的影响。结果表明：（1）干旱胁迫造成油菜实际光化学效率（ФPSⅡ）、表观光合电子传递速率（ETR）、光化学淬灭系数（qP）、净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、蒸腾速率（Tr）均下降,且随干旱时间延长而降低。PSⅡ反应中心完全关闭时荧光产量(Fm）、最小荧光（Fo）随干旱时间延长而升高。PSⅡ原初光能转化效率（Fv/Fm）、PSⅡ的潜在活性（Fv/Fo）相对变化小,下降不显著。（2）干旱后复水1～2周时,油菜气体交换参数较前期干旱处理均有升高,复水2周后升高幅度大于1周,尤其是干旱2周处理后复水时参数值大幅度升高;复水3周时,油菜气体交换参数呈下降趋势,净光合速率明显下降。（3）干旱后复水1～2周时,油菜PSⅡ、ETR、qP值较对照均有升高,复水1周后较2周后的升高幅度大,尤其是干旱2周处理后复水时,它们的升高幅度大于干旱1周处理后复水的情形;Fm、Fo较对照仍有升高,复水3周各荧光参数值下降。复水后Fv/Fm、Fv/Fo值变化相对较小。     

土壤干旱胁迫对白芥光合器官发育及光合速率的影响

利用旱棚盆栽研究了在土壤干旱胁迫下白芥抗旱和不抗旱品系的单叶面积,单株叶面积、出叶速度、叶绿素含量和和净光合速率。结果表明,在土壤干旱胁迫下不同白品系在不同生育时期的单叶面积、单株叶面积、出叶速度及净光合速率都下降,在一定土壤水分范围内,叶绿素含量随土壤水分的下降而增加,抗旱性强的品系受土壤干旱胁迫的影响较小。     

Genetic differences in water-use efficiency,stomatal conductance and carbon isotope fractionation in potato

Summary Potato (Solanum tuberosum L.) cultivars were grown in pots and containers under a rain shelter to examine differences in stomatal conductance, water-use efficiency, and carbon isotope fractionation. Conductance was measured on abaxial leaf surfaces with a steady state diffusion porometer. Carbon isotopic analyses were made with an isotope ratio mass spectrometer. Water-use efficiency (WUE) was obtained by dividing total dry matter production by cumulative transpiration. Significant genetic variation was observed for each trait. WUE was positively related to carbon isotope fractionation (¹³∈) and was inversely related to stomatal conductance. Carbon isotope analysis and porometry show potential as indirect screening methods to identify genetic differences in water-use efficiency.     

Stomatal resistance of three potato cultivars as influenced by soil water status, humidity and irradiance

Summary Leaf stomatal resistance varies considerably in response to changes in environmental conditions. Understanding cultivar differences in the response of stomata to these conditions is important for effectively simulating water-use and growth. In this study the stomatal resistance of three field grown potato (Solanum tuberosum L.) cultivars Atlantic. Monona and Norchip was observed in response to photosynthetic photon flux density, leaf to air vapour pressure difference and root zone available soil water. Substantial variation in stomatal resistance was accounted for by functions of the environmental variables for both Monona and Norchip. The explained variation for Atlantic was considerably less. Light saturation occurred near 500 μmol m⁻² s⁻¹. Increasing stomatal resistance above 1000 μmol m⁻²s⁻¹ was also observed but is likely an artifact of stomatal closure on days in which mid-day leaf water potentials dropped below critical levels. Although the leaf presumably insufficient to obtain substantial effects. The soil water status was partially linked to the average 1000 h to 1500 h stomatal resistance on clear, sunny days. Significant differences were observed among the cultivars in the response of stomata to changes in the available soil water.     

NaCl胁迫对续随子离子吸收及荧光特性的影响

以续随子为材料采用温室盆栽法,研究了NaCl胁迫处理对其生长发育、离子分布和叶绿素荧光特性的影响。结果表明：(1) 25mmol•L-1 NaCl胁迫时续随子幼苗的鲜重、干重和株高比对照略有下降,但不显著;随着NaCl浓度的继续增加,三指标均显著降低。(2)盐胁迫影响植物组织的离子分布,Na +浓度增加时,K+、Ca2+和Mg2+浓度均持续下降,K+/ Na+、Ca2+/ Na+、Mg2+/ Na+ 也急剧下降。(3) NaCl胁迫下,续随子幼苗叶片的初始荧光(Fo)、最大荧光(Fm)、PSⅡ实际光化学效率均降低。但在0～25 mmol•L-1NaCl浓度下,Fo、Fm与对照差异不显著。可见,NaCl胁迫下,续随子产生了光合作用的光抑制伤害。     

玉米耐旱遗传育种研究及分子育种策略

干旱胁迫一直是玉米产量损失的重要逆境因素。本文结合最新玉米组学研究成果,高通量的数据信息分析平台,从玉米表型和基因型两方面重点讨论耐旱玉米在遗传及育种实践上的研究进展,分子育种技术在进行耐旱玉米新品种的选育过程中的新策略,利用新的技术和平台进行耐旱玉米的创新,为未来提高育种遗传增益以及玉米增产稳产起到重要作用。     

梯度干旱胁迫对水稻叶片光合和水分状况的影响

采用温室营养液培养方式,通过添加0%、10%、20%、30%PEG6000模拟干旱胁迫,对水稻幼苗叶片的光合作用和水分状况进行比较分析。结果表明:1)在干旱胁迫下,水稻叶片的光合速率、气孔导度、叶肉导度、总导度和叶绿体内CO2浓度等都显著降低;2)在干旱胁迫条件下,限制光合作用的非气孔限制值并没有显著提高,而气孔限制值则大幅提高;与正常水分条件相比,扬稻6号和汕优63在30%PEG干旱胁迫下气孔限制值分别提高了42%和81%;3)光合速率与气孔导度、叶肉导度、总导度及叶绿体内CO2浓度呈正相关;4)在重度干旱胁迫下(20%和30%),叶片水势和含水量都显著下降,并且叶片水势与气孔导度、叶肉导度和总导度呈正相关。因此,气孔关闭导致的叶绿体内CO2浓度降低是限制光合作用的最主要因素,同时叶片水势的降低增加了叶片内CO2传输的阻力。     

Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). II. Relations between plant growth and measurements of fluorescence

Summary Relations between measurements of the slow kinetics of chlorophyll fluorescence and growth and yield were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Drought reduced total dry matter production and yields and increased tuber dry matter concentration. Drought increased harvest index in cv. Spunta, but decreased it in cv. Pentland Crown. Total dry matter production was correlated with each of constant fluorescence, variable fluorescence and the half life of the decay in variable fluorescence. These correlations were determined largely by the effect of treatment, and did not discriminate effectively between genotypes within a treatment.     

Varietal differences in the response of potatoes to repeated short periods of water stress in hot climates. 1. Turgor maintenance and stomatal behaviour

Summary The response of six potato cultivars, Désirée, Up-to-Date, Alpha, Elvira, Spunta and Troubadour, to water stress under high ambient temperatures was investigated. Osmotic regulation in the leaves of all six cultivars was highest in Alpha and the lowest in Troubadour. Concomitantly, Alpha maintained the highest turgor potential under water stress while Troubadour had the lowest values indicating a relationship between the degree of osmotic regulation and maintenance of turgor. The highest stomatal conductance under water stress was exhibited by Désirée while both stressed and non-stressed plants of Up-to-Date had the lowest values. In addition, Up-to-Date had a larger root system than Désirée. The association of these traits with tolerance to short periods of drought in the potato is discussed. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No 295-E, 1981 series. The investigation was supported in part by a grant from the Ministry for Development Cooperation of the Netherlands.     

Yield response of potato genotypes to different soil water regimes in contrasting seasons of a subtropical climate

Summary Potato crops in subtropical climates are often subjected to water stress, resulting in low yields and poor tuber quality. The yield response of potato genotypes to water supply was investigated in six trials, three each in spring and autumn plantings. Trials were conducted under automated rain shelters, using an irrigation boom to impose five soil water regimes. The negative effect of water stress on tuber yield was more detrimental in spring than in autumn, because of higher atmospheric evaporative demand and higher temperatures in spring. An average yield reduction of 68% was recorded for the most severely stressed regime in spring plantings, while the mean reduction for the same treatment in autumn was only 42%. Genotypic differences in yield response to drought were clearly illustrated in spring, but not in autumn. This suggests that the choice of genotypes is only influenced by the availability of water in spring, when more drought tolerant genotypes should be used.     

Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color

Potatoes grown for processing in irrigated regions of the Pacific North-west sometimes develop undesirably high concentrations of reducing sugars in tuber stem ends due to hot weather and water stress during tuber development. Such tubers usually produce french fries with dark stem ends or sugar ends. In order to better quantify the relationship between water stress and stem-end sugar levels for Russet Burbank, single episodes of transitory water stress were established by delaying irrigations until soil water potentials ranging from -32 to -107 kPa were reached during early tuber bulking. To determine when the increase in reducing sugars occurred, tubers were sampled before transitory stress, at maximum stress, after stress was relieved with sprinkler irrigation, and post harvest. Reducing sugar concentrations did not increase in tuber stem ends until two weeks or longer after the plant water stress was relieved. Increased reducing sugar concentrations were positively associated with decreased soil water potential (drier soil). Tubers were sliced and fried at harvest and six weeks post-harvest. Decreasing soil water potential (drier soil) was associated with progressively darker fry colors at harvest and post harvest. Significant darkening in the average stem-end fry color light reflectance of tubers at harvest as observed at -80 kPa in 1988 and -69 kPa in 1989. The effect of imposed water stress on tuber stem-end reducing sugar concentrations was most pronounced post harvest.     

Characteristics of photosynthesis and conductance of potato canopies and the effects of cultivars and transient drought

Gas-exchange characteristics of potato (Solanum tuberosum L.) canopies were determined with crop enclosures under condition of optimal water supply, during soil water depletion, and during recovery from drought-stress. The plants were grown under a rainshelter in large containers with 2-m² surface area. Control plants received water throughout the growth period. In Expt. 1, transient drought was imposed by interrupting water supply completely for 22 days. During the 33-day period of drought treatment in Expt. 2, the stressed plants received half the amount of water that was given to the control plants (irrigations 2–3 times per week).

During soil water depletion, stomatal conductance of the canopy was reduced earlier and more than photosynthesis. This resulted in a lower internal carbon dioxide concentration in the leaves of stressed plants and a higher ratio between photosynthesis and stomatal conductance. The value of that ratio increased as soil water potential dropped.

Water-use efficiency ( ) increased during drought stress. The cultivar Bintje showed a larger ratio between photosynthesis and stomatal conductance of the canopy and a higher than cv. Saturna, both for optimal water supply and during drought stress.

Photosynthesis and conductance of the canopy started to recover immediately upon rewatering, even when relative values had declined to 20–30% during the preceding stress period. After release from stress, the leaves in the top layer of the canopy had a higher stomatal conductance in treated plants than in control plants.     

Selection of grazing-tolerant lucerne cultivars

Improvement of grazing-tolerance in lucerne ( Medicago sativa L.) is an objective of interest worldwide for the acknowledged potential of this species in pastures. A breeding programme applied standard methods of the selection for this trait, which implies continuous stocking and intensive grazing, to germplasm preliminarily selected for reportedly positive morphological attributes (large and deep crowns; non-erect growth habit). In this study six experimental cultivars, originating from this programme, and three check varieties were evaluated. Grazing tolerance was assessed under continuous sheep stocking for 2 years. Herbage yield in 3 years and seed yield (in the second year) were also evaluated in distinct and contiguous sub-experiments. One experimental cultivar had a prostrate habit, two were semi-prostrate, and three were semi-erect. Under grazing, five of them showed final persistence similar to, or better than, that of the tolerant check variety adopted in the standard test. In particular, the prostrate experimental cultivar (termed Camporegio) had remarkable persistence, although associated with low vigour, associated with the introgression of M. sativa ssp. falcata into its parentage. A semi-erect cultivar (termed Verbena) possessed a good balance between grazing tolerance, potential dry-matter yield and seed yield.     

Assessment of the frost sensitivity of wild and cultivated potato species by chlorophyll fluorescence analysis

Summary The potential of the chlorophyll fluoresence technique in screening for frost sensitivity in seedling progenies representing 18 genotypes of wild and cultivated potato from different geographical and altitudinal origins was assessed by measuring the decrease in variable chlorophyll fluorescence (F_var) of terminal leaflets of hardened and non-hardened plants after freezing at −5°C for 60 min and subsequent re-warming to 20°C. The method was rapid and the results obtained agreed well with a visual assessment of frost injury carried out after leaflets had been returned to optimal growth conditions for 72 hours.Solanum tuberosum CPC 3294 originating from Chile was the most frost-sensitive genotype studied andSolanum albicans CPC 3712 from high-altitude regions of Peru, the most frost-resistant. Frost damage increased with length of exposure to frost and this was associated with a reduction of variable fluorescence and quenching capacity of the thylakoid membranes.

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Zusammenfassung An S?mlingsnachkommen, die 18 Genotypen wilder und kultivierter Kartoffelarten aus verschiedenen geographischen Herkünften und H?henlagen repr?sentierten, wurde die Eignung der Chlorophyll-Fluoreszenztechnik zur Prüfung auf Frostempfindlichkeit untersucht, in dem die Abschw?chung bei der variablen Chlorophyll-Fluoreszens (F_var) an den endst?ndigen Fiederbl?ttern abgeh?rteter und nicht-abgeh?rteter Pflanzen nach 60 minütigem Abkühlen auf −5°C und anschliessender Erw?rmung auf +20°C gemessen wurde (Abb. 1). Diese Methode war schnell, und die damit erhaltenen Ergebnisse stimmten gut mit einer visuellen Beurteilung der Frostsch?den nach dem Zurückbringen der Bl?ttchen für 72 Stunden in optimale Wachstumsbedingungen, 15°C/10°C (Tag/Nacht), überein. Die visuelle Beurteilung der Besch?digung basierte auf den Schadsymptomen wie Chlorosen, w?sserigen Flecken und nekrotischen Bereichen, ausgedrückt in Prozenten der beeintr?chtigten Fiederblattfl?che und korrigiert an Hand der nicht-gekühlten Kontrolbl?ttchen. Die aus Chile stammendeSolanum tuberosum CPC 3294 erwies sich als der Genotyp mit der h?chsten Frostempfindlichkeit undSolanum albicans CPC 3712 aus den hohen H?henlagen Perus als derjenige mit der h?chsten Frostresistenz (Tab. 1). Der Frostschaden nahm mit der Dauer der Frosteinwirkung zu und war verbunden mit einer Reduktion der variablen Fluoreszenz und der Quench-Kapazit?t der Thylakoidmembranen (Abb. 3). Diese Ergebnisse weisen darauf hin, dass das starke Zerreissen der Thylakoid-membranen durch das Gefrieren verursacht wird (Tab. 2). Ferner wurde gefunden, dass die 10-t?tige Frostabh?rtung bei 4°C/2°C (Tag/Nacht) vor dem Versuch nur eine geringe Wirkung auf die Reduktion des durch die Thylakoidmembranen entstandenen Schadens hatte, mit Ausnahme verschiedener chilenischer Sorten vonSolanum tuberosum (CPC 5374, CPC 5646, CPC 5643, CPC 3294) (Tab. 1). Die Abbildung 4 zeigt die ?nderungen im F_R (Rate des Fluoreszenzanstiegs) nach dem Gefrieren bei −5°C. Wenn diese Technik auch nicht alle anderen gegenw?rtig verwendeten Frostunter-suchungsmethoden v?llig zu ersetzen vermag, so sollte sie doch von den Pflanzenzüchtern als ein zus?tzliches Instrument betrachtet werden, um bei Pflanzen K?ltesch?den abzusch?tzen.

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Résumé La sensibilité au gel de plantules issues de 18 génotypes comprenant des espèces sauvages et cultivées de pommes de terre est étudiée par mesure de la diminution de fluorescence chlorophyllienne (F_var) des folioles apicales sur des plantes durcies ou non après passage au froid à −5°C pendant 60 minutes suivi d'un réchauffement à 20°C (figure 1). La méthode est rapide et les résultats obtenus sont comparables aux notations visuelles des dégats de gel, lorsque les folioles sont mises en condition optimale de croissance: 15 °C/10 °C (jour/nuit) pendant 72 heures (figure 2). Pour la notation visuelle, les observations portent sur les sympt?mes tels que les chloroses, les poches d'eau et les zones nécrotiques, exprimés en pourcentage de surface endommagée par rapport au témoin non gelé.Solanum tuberosum, CPC 3294, d'origine chilienne, s'avère être le génotype testé le plus sensible etSolanum albicans, CPC 3712, originaire des hauts-plateaux péruviens, le génotype le plus résistant (tableau 1). L'endommagement par le gel augmente avec la durée d'exposition au gel et cela correspond à une diminution de fluorescence et de capacité d'étanchement des membranes thylako?des (figure 3). Ces résultats montrent qu'un éclatement réel des membranes thylako?des est induit pendant le gel (tableau 2). Un durcissement à 4°C/2°C (jour/nuit) pendant 10 jours avant l'expérience a peu d'effet sur le niveau d'endommagement maintenu par les membranes thylako?des, à l'exception de quelques variétés chiliennes deSolanum tuberosum (CPC 5374; CPC 5646; CPC 5643; CPC 3294) (tableau 1). La figure 4 montre les changements de F_R (taux d'augmentation de fluorescence) après le gel à −5°C. Bien que cette technique ne puisse remplacer totalement les méthodes utilisées jusqu'à ce jour, elle peut servir de complément d'analyse dans la recherche de variétés sensibles aux basses températures.

     

不同水分处理对甘蔗光合作用的影响

甘蔗伸长期间，智能模拟自然降雨，进行降雨量为60、40、20、0mm／旬的水分处理。试验结果表明：0mm／旬处理＋1叶的叶绿素含量、气孔导度、胞间CO2浓度、蒸腾速率、净光合速率很低；各灌水处理中，40mm／旬处理的叶绿素含量、气孔导度、胞间CO2浓度、蒸腾速率、净光合速率高而稳定。