植物抗寒性的研究进展

温度过低会对植物造成一定的伤害,并引起植物体内一系列的生理生化反应,本文综述了植物寒害类型、抗寒基因、冷冻伤害及低温驯化后植物的生理生化变化等方面的研究进展。     

经济植物的抗寒性研究进展

综述了植物抗寒研究的新进展。植物在低温下的抗寒生长过程中，其形态结构及其超显微结构发生变化．膜脂的成分及蛋白质数量和种类也发生改变；植物的抗寒生理生化的变化是通过低温改变基因表达而引发的，在抗寒中起作用的基因已经识别出来，并且已经了解这些基因的作用方式．ABA和PP333等外源激素和钙离子能诱导植物体内的ABA水平提高，从而增强植物的抗寒能力。但诱导机理仍待研究。     

植物的冷调节蛋白及诱导其基因表达的条件

人们发现植物在低温锻炼过程中产生的特异性蛋白——冷调节蛋白(coldregulatedproteins,CORPs)与植物的抗寒力密切相关.冷调节基因是一些诱导型表达基因,它们除受低温诱导外,还能接受诸如外源ABA、水分胁迫等外界条件的诱导.在综述这些诱导冷调节基因表达条件的基础上,提出了在低温寒害来临之前有目的地诱导大田植物冷调节基因表达,合成冷调节蛋白,可提高植物抗寒力的新思路.这在农业生产以及园艺植物南树北移工作中具有重要的现实意义.     

CBF转录因子及其在林木抗寒研究中的应用前景

CBF转录因子是一类受低温诱导的反式作用因子,广泛存在于各种植物中。它可以与启动子中CRT/DRE顺式作用元件特异结合,激活其下游冷应答基因COR的表达,从而提高植物的抗寒性。自CBF1基因被发现以来,关于CBF基因结构及功能方面的研究已有很多报道,为提高植物的抗寒性和培育抗逆新品种提供理论依据。该文介绍了CBF基因家族的结构特点、表达调控及抗寒作用机制,并展望了其在林木抗逆研究中的应用前景。     

11个南竹北移竹种抗寒性差异

利用半致死温度(LT₅₀)探讨不同竹种间抗寒性及冷驯化能力,筛选抗寒能力强、冷驯化能力佳的竹种,为我国“南竹北移”竹种选择、抗寒竹种引种等工作提供科学依据。以从江苏扬州引种至山东的11个竹种为试验材料,采用电导法配合Logistic方程推算各竹种的低温半致死温度。结果表明：11个竹种在来源地江苏的抗寒性强弱排序依次是：金镶玉竹>早园竹>毛金竹>黄纹竹>四季竹>阔叶箬竹>茶秆竹>乌哺鸡竹>大明竹>斑苦竹>紫竹;在引种地山东的抗寒性排序是：金镶玉竹>茶秆竹>大明竹>早园竹>黄纹竹>四季竹>乌哺鸡竹>毛金竹>斑苦竹>阔叶箬竹>紫竹。11个供试竹种中抗寒能力最强的是金镶玉竹,经引种地的低温驯化后,冷驯化能力最强的是大明竹,其次是茶秆竹和斑苦竹;最弱的是毛金竹和阔叶箬竹,未表现出冷驯化能力。     

不同杨树抗寒性生理指标评价

通过对低温条件下不同杨树枝条的渗透调节物质含量、酶活性等生理指标的测试,研究了其对低温的适应性以及抗寒能力的强弱。结果表明,在相同立地条件下不同杨树的8个抗寒生理指标,均表现出显著性差异水平,说明在低温条件下杨树抗寒力的形成与膜保护系统和渗透调节物的积累密切相关。经模糊数学隶属函数值法对其抗寒性进行综合评价,得出抗寒性以银×新抗寒最强。     

6种常绿阔叶植物耐寒性综合评价

为改变冬季北方园林的萧条景象,实现常绿阔叶树种在北方的引种驯化,在低温胁迫条件下,测定了6种常绿阔叶树种红叶石楠、扶芳藤、常春藤、法国冬青、北海道黄杨和枸骨的膜透性变化,可溶性糖、可溶性蛋白和脯氨酸三种渗透调节物质含量的变化,超氧化物歧化酶活力的变化程度,并运用隶属函数法综合评价了其抗寒能力的强弱,为常绿树种在北方的引种驯化提供依据。研究结果表明:随着温度的下降,各供试材料叶片的膜透性增大,可溶性糖、可溶性蛋白和脯氨酸积累量增多,超氧化物歧化酶活性增强。隶属函数法抗寒性综合评价显示北海道黄杨、扶芳藤、常春藤的抗寒能力较强,红叶石楠和枸骨抗寒能力中等,法国冬青抗寒性弱。     

磷对慈竹抗寒性的影响研究

随着全球气候变化加剧,增强植物抗逆性日益成为一个重要的研究课题.施肥作为速生丰产人工林培育的主要手段,其对竹类植物的抗寒性影响方面的研究甚少.本实验以慈竹为材料,研究低温胁迫下不同磷肥施用水平对其抗寒性的影响,旨在确定提高慈竹抗寒性的最佳施肥水平,以期为应对全球气候变化的极端天气提供参考.结果表明,随着温度的降低,慈竹各抗寒生理指标呈现规律性变化,磷肥施用量对慈竹抗寒性有明显的影响.在氮、钾肥施用量适中时,施用低水平磷肥(1.25kg丛·年)更有利于提高慈竹的抗寒性.     

DREB/CBF基因响应植物抗冷途径的研究进展

低温环境信号通过细胞膜的转导,激活以DREB/CBF途径为主的抗冷信号网络,调控下游大量抗冷功能基因的表达,继而增强植物的抗冷能力。本文重点介绍了国内外近年来有关CBF基因结构特点、CBF转录因子在植物抗逆基因工程中的作用,CBF信号途径的研究包括Ca2+与低温信号转导、CBF转录因子在植物抗冷过程中的表达调控、生物节律调控CBF转录因子的表达等方面,旨在为植物抗逆育种提供理论依据。     

低温胁迫下植物光合生理研究进展

低温胁迫下,植物通过一系列生理过程变化来提高自身生态适应性,本文综述了植物应对低温胁迫时,其光合作用、膜系统、渗透调节、保护酶系统的生理响应,系统探讨胁迫发生机理,为植物克服并适应低温胁迫,选育抗寒性较强的品种提供理论依据。     

Differential responses of silver birch (Betula pendula) ecotypes to short-day photoperiod and low temperature

We investigated interrelations of dormancy and freezing tolerance and the role of endogenous abscisic acid (ABA) in the development of silver birch (Betula pendula Roth) ecotypes in controlled environments. Short-day treatment induced growth cessation, bud set and dormancy development, as well as initiation of cold acclimation and an increase in freezing tolerance. Subsequent low temperature and short days (12-h photoperiod) resulted in a significant increase in freezing tolerance, whereas bud dormancy was gradually released. The concentration of ABA increased in response to short days and then remained high, but ABA concentrations fluctuated irregularly when the dormant plants were subsequently exposed to low temperature during short days. Although there was a parallel development of freezing tolerance and bud dormancy in response to short days, subsequent exposure to low temperature had opposite effects on these processes, enhancing freezing tolerance and releasing dormancy. Compared with the southern ecotype, the northern ecotype was more responsive to short days and low temperature, exhibiting earlier initiation of cold acclimation, growth cessation and an increase in ABA concentrations in short days, and higher freezing tolerance, faster dormancy release and greater alteration in ABA concentrations when subsequently exposed to low temperature during short days. The rates and extent of the increases in ABA concentration may be related to increases in freezing tolerance and dormancy development during short days, whereas the extent of the fluctuations in ABA concentration may play an important role in enhancing freezing tolerance and releasing dormancy during a subsequent exposure to low temperature during short days.     

Different responses of northern and southern ecotypes of Betula pendula to exogenous ABA application

We investigated responses of northern and southern ecotypes of silver birch (Betula pendula Roth) to exogenous abscisic acid (ABA) under controlled environmental conditions to determine the role of ABA in cold acclimation and dormancy development. Abscisic acid was sprayed on the leaves and changes in freezing tolerance, determined by the electrolyte leakage test, and bud dormancy were monitored. Applied ABA induced cold acclimation but had no effect on growth cessation in seedlings grown in long day conditions (LD, 24-h photoperiod at 18 degrees C). It enhanced freezing tolerance and accelerated growth cessation in seedlings grown in short day conditions (SD, 12-h photoperiod at 18 degrees C), and slightly enhanced freezing tolerance in seedlings grown at low temperature (LT, 24-h photoperiod at 4 degrees C) in both ecotypes. There were distinct ecotypic differences in ABA-induced cold acclimation and dormancy development. The northern ecotype was more responsive to applied ABA than the southern ecotype, resulting in more rapid development of freezing tolerance in all treatments, and earlier dormancy development in SD. When plants were grown in a photoperiod just above the critical photoperiod for the ecotype (defined as the longest photoperiod that induces growth cessation), applied ABA caused growth cessation and dormancy development. Compared with ABA-treated seedlings grown in SD, dormancy development was delayed in ABA-treated seedlings exposed to a near-critical photoperiod, but even in this treatment dormancy developed faster in the northern ecotype than in the southern ecotype.     

Frost hardening and dehardening in Abies procera and other conifers under differing temperature regimes and warm-spell treatments

Frequent bud frost damage in cultivation of Abies procera Rehderand pending climate changes are the background for this studyof cold hardiness under varying acclimation regime (in closed-topchambers) and experimental warm spells during the cold season.LT₅₀ values were established by freezing tests at differenttimes of year. Damage and deaths were assessed on leader buds,subapical lateral buds, needles and cambium. Minor parallelexperiments involved Abies nordmanniana, Picea abies and Piceasitchensis. Lower acclimation temperatures resulted in deeperfrost hardiness during late autumn but less during spring, comparedwith ambient temperature controls. Elevated temperatures resultedin less deep frost resistance. Apical buds generally developeddeeper frost hardiness than lateral buds but less deep thanthe cambium, varying with species, however. Frost damage inbuds ranged from death over partially destroyed bud contentsresulting in distorted shoots to buds seemingly remaining dormant.Responses to warm spells differed with duration, timing andspecies, ranging from dramatic decrease in frost hardiness withor without subsequent recovery to no reaction. Furthermore,the reactions did not show any clear relation to dormancy level.For A. procera, exposure to fluctuating temperatures appearedto be particularly problematic. This explains why this speciesdevelops best in coastal climates, and in sites sheltered fromtemperature extremes either by hedging, a winter snow cover,or topography. The Christmas tree production will suffer severelyon sites with harsh temperatures due to losses of lateral andterminal buds, which destroy the crown symmetry. Clipping ofgreenery is less influenced by frost damages, although the developmentof normal branch whorls is often disturbed.     

低温对园林植物体内渗透物质与丙二醛含量的影响

随着地球温室效应的增加，世界各地极端天气不断出现，极端低温是重要的一种表现形式，而极端低温会对园林植物造成极大的伤害。园林植物为抵御低温的伤害，其体内会发生一系列的生理生化变化，其中，渗透物质含量的变化可以反映园林植物抗寒性的强弱，而丙二醛含量直接反应树体受低温伤害的程度。作者列举了大量的试验研究结果，详细分析了低温影响下园林植物体内可溶性蛋白，可溶性糖，游离脯氨酸含量的变化规律，同时，分析了园林植物体内丙二醛含量的变化情况，为合理判断园林树木抗寒性强弱、园林植物引种以及养护提供理论支持。     

Effects of "near-lethal" stress on bud dormancy and stem cold hardiness in red-osier dogwood

We studied the effects of "near-lethal" (NL, 47 degrees C for 1 h) heat stress, applied to intact shoots of red-osier dogwood (Cornus sericea L.) during early (October), deep (November) or late (December) dormancy, on bud dormancy release and development of stem tissue cold hardiness under natural conditions and at a constant temperature of 0 or 23 degrees C in the dark. The NL heat-stress treatment overcame bud dormancy when applied during the early and late stages of dormancy. During October and December, all plants in the 23 degrees C + dark post-stress environment broke bud within 35 and 12 days, respectively, whereas the corresponding values for days to bud break in the control plants were more than 150 and 110 days, respectively. Application of NL heat stress during deep dormancy caused only slightly earlier bud break compared to the control plants. In the 0 degrees C + dark post-stress environment, all NL heat-treated plants died within 9 weeks. Under natural post-stress conditions, bud break in plants receiving NL heat stress during early and deep dormancy occurred at the same time as in control plants, whereas bud break of plants receiving NL heat stress during late dormancy occurred 55 days earlier than in control plants. Under both natural and 23 degrees C + dark post-stress conditions, cold hardiness of plants receiving NL heat stress during early dormancy was similar to that of controls. Application of NL heat stress during deep dormancy hastened the rate of deacclimation under the 23 degrees C + dark post-stress conditions but had no effect on deacclimation under natural post-stress conditions. Application of NL heat stress during late dormancy enhanced deacclimation of plants in both the 23 degrees C + dark and natural post-stress environments.     

Relationships among cold hardiness, root growth potential and bud dormancy in three conifers

Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Stem cold hardiness, total new root length at 14 days and days to bud break were measured weekly. Relationships among cold hardiness, root growth potential (RGP) and bud dormancy suggest that cold hardiness, which can be measured quickly, could provide a useful basis for estimating the two other parameters. During cold acclimation, there was a lag period in which stem cold hardiness remained at -15 degrees C and RGP was at a minimum, in all three species. Douglas-fir and Engelmann spruce buds remained fully dormant during this lag period. Ponderosa pine buds had no chilling requirement for the loss of dormancy, and reached quiescence during the lag period. Immediately following the lag period, as stem cold hardiness progressed to -22 degrees C, RGP increased to a high plateau in all three species, and Douglas-fir and Engelmann spruce buds approached quiescence. Cold deacclimation and bud development began immediately on exposure to warm, long days, but RGP remained high until stem cold hardiness returned to approximately -15 degrees C. At bud break, cold hardiness and RGP were at the minimum.     

常绿树种在越冬过程中光合速率的变化及其对低水势的反应

树木叶片的耐旱力因树种不同而异,也因树体的生长时期、在树冠上的部位和环境条件的不同,不断地变化。在自然生境和生长状况下,耐旱力的可靠指标怎样才能取得,目前尚未见到快速有效的测定方法。我们试图根据在模拟干旱(低水势的甘露醇溶液)条件下,叶片光合放氧受抑制程度的判定、耐旱潜力的比较及其变化规律,常绿树种在越冬过程中耐寒力与渗透调节能力的变化密切相关性,来弄清叶片耐寒力与耐旱力的变化是否也是同步的。