濒危树种越南青冈的半致死温度研究

越南青冈为壳斗科濒危树种。通过越南青冈2年生温室容器苗叶片和茎段分别在9个高温和8个低温温度处理后，测定其电解质渗出率，利用Logistic方程计算其高温、低温的半致死温度（ LT50）。结果表明，叶片和枝条组织的电解质渗出率与处理温度之间均呈“S”型曲线， Logistic方程拟合度较高；计算得到越南青冈2年生苗木叶片的高温、低温半致死温度分别为42.04℃和-1.78℃，茎段的高温、低温半致死温度分别为46.62℃和-9.72℃。研究结果可推测越南青冈的潜在地理分布区，为该濒危树种的人工栽培、就地或迁地保护提供依据。     

无柄小叶榕耐寒性研究

采用人工模拟低温处理技术测定无柄小叶榕离体叶片在不同低温梯度胁迫下电解质渗出率的变化,并利用Logistic方程拟合其电解质渗出率的曲线,计算半致死温度(LT50)。结果表明:在低温胁迫处理过程中,随着温度的降低,电解质渗出率与处理温度呈负相关;电解质渗出率整体变化呈典型的"S"形单峰曲线;经显著性检验相关系数均在0.91以上,符合Logistic方程;通过方程拐点确定无柄小叶榕半致死温度为-3.95℃。     

5种屋顶绿化景天属植物耐热性的测定

运用电导率法对5种屋顶绿化景天属植物进行耐热性测定.叶片经梯度高温处理后,处理温度与细胞伤害率之间呈"S"形曲线,经显著性检验符合Logistic方程.通过Logistic拐点确定半致死温度LT50(℃).分别为佛甲草66.17℃、东南景天63.18℃、圆叶景天57.38℃、凹叶景天56.45℃、藓状景天53.25℃.5种景天属植物适合作为屋顶开敞型绿化植物材料,可以解决目前屋顶开敞型绿化植物存在着颜色单调、品种单一等缺陷.     

12个樱花新品种的耐热性研究

樱花是早春重要的观花植物,在城市园林绿化和美丽乡村建设中具有重要的作用.本研究采用电导率法测定了12个樱花新品种叶片在40℃、45℃、50℃、55℃、60℃、65℃、70℃下细胞伤害率的变化,利用Logistic方程,计算出其高温半致死温度(LT50),结合夏季高温后的热害等级数据,进行聚类分析和耐热性评价.结果表明:...     

4种珍稀濒危植物的半致死温度研究

以红皮糙果茶(Camellia crapnelliana)、伯乐树(Bretschneidera sinensis)、金花茶(C.petelotii)、坡垒(Hopea hainanensis)4种珍稀濒危植物1 a生幼苗的成熟叶片为试验材料,进行高温、低温胁迫试验,测定叶片相对电导率,并利用Logistic方程建立回归模型,计算出高温和低温半致死温度。结果表明:在高温胁迫和低温胁迫过程中,相对电导率变化趋势均呈现明显的"S"型曲线,耐热性大小顺序依次为:金花茶红皮糙果茶坡垒伯乐树,高温半致死温度在41.6~46.3℃之间;耐寒性大小顺序依次为:红皮糙果茶坡垒伯乐树金花茶,其低温半致死温度在-7.19~-6.16℃之间。供试的4种珍稀濒危植物1 a生苗均具有较强的耐热性和耐寒性,在广州地区可以安全露地越夏及越冬。研究结果可推测这4种珍稀濒危植物潜在的适应地区,从而扩大引种栽培。     

应用Logistic方程确定巨龙竹叶片低温半致死温度

以云南西盟种源2年生巨龙竹幼苗叶片为研究对象,低温胁迫24 h后测定其不同温度处理下相对电导率,并应用Logistic方程建立回归模型,计算半致死温度。结果表明,随着处理温度的逐渐降低,相对电导率呈"S"型曲线上升,5℃到0℃时相对电导率只是少量增加,从0℃到-5℃时电导率急剧升高,-5℃到-15℃时电导率缓慢升高;应用Logistic方程计算巨龙竹幼苗叶片半致死温度为-2.16℃,相关系数0.907,表明低温胁迫下的相对电导率遵循Logistic方程的变化规律。     

应用Logistic方程确定三种桉树的低温半致死温度

以3种桉树幼苗叶片为实验材料,以电导法测定低温胁迫下其叶片的电导率变化并配以Logistic方程进行回归分析,发现不同低温下的电导率遵循Logistic方程的变化规律,且与半致死温度呈线性关系,依据回归方程计算得到尾叶桉(E.urophylla)、巨桉(E.grandis)和邓恩桉(E.dunnii)的拐点半致死温度分别为-4.53℃、-8.12℃、-7.79℃.     

邯郸地区15种常绿阔叶树种抗寒性比较

以邯郸地区引种的15种主要常绿阔叶树种的叶片为试材,经过-5℃、-10℃、-15℃、-20℃、-25℃、-30℃冷冻处理,测定其在不同低温处理下的电导率,再利用Logistic方程计算各树种的半致死温度,以确定这些树种抗寒力的相对强弱.结果表明:各树种相对电导率均随温度降低而有不同程度的提高,上升趋势呈"S"型曲线.根据半致死温度确定的各树种抗寒力的相对强弱.与各树种在当地越冬状况基本一致.     

5种木本花卉对高低温的耐受性

以石斑木(Rhaphiolepis indica)、臀果木(Pygeum topengii)、桃叶石楠(Photinia prunifolia)、香蒲桃(Syzygium odoratum)、肖蒲桃(Syzygium acuminatissimum)等5种木本花卉1年生幼苗的叶片为试验材料,进行不同梯度高温和低温胁迫,测定叶片浸出液的电导率,并利用Logistic方程建立回归模型,计算高温和低温半致死温度。结果表明:在高温胁迫过程中,5种木本花卉的相对电导率均随温度的上升而持续上升,耐热性大小顺序依次为:香蒲桃石斑木肖蒲桃桃叶石楠臀果木,高温半致死温度在42.81~48.66℃之间;在低温胁迫过程中,5种木本花卉的相对电导率均随温度的降低而持续上升,耐寒性大小顺序依次为:臀果木石斑木肖蒲桃桃叶石楠香蒲桃,其低温半致死温度在-8.54~-6.07℃之间。5种新优木本花卉均具有较强的抗热性和抗寒性,在广州地区可以安全露地越夏和越冬,可在节约型园林建设中适当的选择和配置。     

４种珍稀濒危植物的半致死温度研究

以红皮糙果茶（Camellia crapnelliana）、伯乐树（Bretschneidera sinensis）、金花茶（C．petelotii）、坡垒（Hopea hainanensis）4种珍稀濒危植物1 a 生幼苗的成熟叶片为试验材料,进行高温、低温胁迫试验,测定叶片相对电导率,并利用 Logistic 方程建立回归模型,计算出高温和低温半致死温度。结果表明：在高温胁迫和低温胁迫过程中,相对电导率变化趋势均呈现明显的“S”型曲线,耐热性大小顺序依次为：金花茶＞红皮糙果茶＞坡垒＞伯乐树,高温半致死温度在41．6～46．3℃之间;耐寒性大小顺序依次为：红皮糙果茶＞坡垒＞伯乐树＞金花茶,其低温半致死温度在－7．19～－6．16℃之间。供试的4种珍稀濒危植物1 a 生苗均具有较强的耐热性和耐寒性,在广州地区可以安全露地越夏及越冬。研究结果可推测这4种珍稀濒危植物潜在的适应地区,从而扩大引种栽培。     

Salt tolerance of frost-resistant eucalypts

Nineteen frost-resistant Eucalyptus species were screened for salt tolerance under glasshouse conditions. This study was undertaken in order to determine the potential of these species for planting on dryland salt-affected sites in the frost-prone Tablelands of south-eastern Australia. Seedlings were established in sand-filled pots and exposed to a step-wise increase in NaCl concentration to a maximum of 500 mol m^–3. Salt tolerance was assessed on the basis of mortality, leaf damage and height growth. All species in the subgenus Symphyomyrtus , particularly those in the Section Maidenaria Series Ovatae, were moderately salt-tolerant (no mortality at 300 mol m^–3 NaCl) whereas those in the subgenus Monocalyptus proved to be very salt-sensitive (no survival at 300 mol m^–3 NaCl). Eucalyptus camaldulensis, E. tereticornis and E. occidentalis were the most salt-tolerant species of those included in this study. Salt-sensitive species had shoot Na⁺ and Cl^– concentrations of up to 2.25 mmol g^–1 dry wt.

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花绒寄甲耐寒性研究

花绒寄甲是天牛类林木蛀干害虫的主要天敌昆虫。文章研究了野生花绒寄甲种群和室内饲养种群的过冷却点,并对其野外栖息的树体内洞穴的温度进行了监测,比较了树体内外温度差异。结果显示,花绒寄甲野生种群的过冷却点平均为-23.9℃,最低可达到-27.3℃。室内饲养种群的耐寒能力较差,平均过冷却点为-15.9℃,最低为-23.8℃。对提高饲养种群耐寒性品质提出了建议。在冬季,花绒寄甲野外栖息的树体内洞穴的温度略高于树体外的气温,能为花绒寄甲越冬成虫营造较好的微栖境。     

邓恩桉等6种桉树的耐寒能力研究

通过对在江西北部试验地的温度记录及对6个桉树树种其9个品种的耐寒表现进行研究,发现了试验地的气温变化特点,并判断极限低温、不充分的耐寒锻炼是导致桉树寒害的主要原因;在-6.8℃低温中,本沁桉、溪谷桉的耐寒能力强,多利桉与邓恩桉具有一定的耐寒力,柳桉和巨桉不具有耐寒能力。选择出耐寒能力与速生性均优良的邓恩桉20748种源、本沁桉为推荐发展的品种。     

乌桕幼苗耐旱性研究

采用PEC,6000模拟干旱胁迫和自然干旱胁迫两种方法,通过测定土壤含水量、叶片电导率、叶片丙二醛含量等指标,分析比较不同品种乌桕幼苗在干旱胁迫下的生理生化变化及耐旱性。结果表明：鸟桕幼苗优13和优24耐旱性较强,优23子代幼苗耐旱性最弱。PEC6000模拟干旱胁迫与自然干旱胁迫试验结果基本一致,可以在一定程度上反映正常的干旱胁迫。     

Freezing tolerance of conifer seeds and germinants

Survival after freezing was measured for seeds and germinants of four seedlots each of interior spruce (Picea glauca x engelmannii complex), lodgepole pine (Pinus contorta Dougl. ex Loud.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata Donn ex D. Donn). Effects of eight seed treatments on post-freezing survival of seeds and germinants were tested: dry, imbibed and stratified seed, and seed placed in a growth chamber for 2, 5, 10, 15, 20 or 30 days in a 16-h photoperiod and a 22/17 degrees C thermoperiod. Survival was related to the water content of seeds and germinants, germination rate and seedlot origin. After freezing for 3 h at -196 degrees C, dry seed of most seedlots of interior spruce, Douglas-fir and western red cedar had 84-96% germination, whereas lodgepole pine seedlots had 53-82% germination. Freezing tolerance declined significantly after imbibition in lodgepole pine, Douglas-fir and interior spruce seed (western red cedar was not tested), and mean LT50 of imbibed seed of these species was -30, -24.5 and -20 degrees C, respectively. Freezing tolerance continued to decline to a minimum LT50 of -4 to -7 degrees C after 10 days in a growth chamber for interior spruce, Douglas-fir and lodgepole pine, or after 15 days for western red cedar. Minimum freezing tolerance was reached at the stage of rapid hypocotyl elongation. In all species, a slight increase in freezing tolerance of germinants was observed once cotyledons emerged from the seed coat. The decrease in freezing tolerance during the transition from dry to germinating seed correlated with increases in seed water content. Changes in freezing tolerance between 10 and 30 days in the growth chamber were not correlated with seedling water content. Within a species, seedlots differed significantly in freezing tolerance after 2 or 5 days in the growth chamber. Because all seedlots of interior spruce and lodgepole pine germinated quickly, there was no correlation between seedlot hardiness and rate of germination. Germination rate and freezing tolerance of Douglas-fir and western red cedar seedlots was negatively correlated. There was a significant correlation between LT50 after 10 days in the growth chamber and minimum spring temperature at the location of seedlot origin for interior spruce and three seedlots of western red cedar, but no relationship was apparent for lodgepole pine and Douglas-fir.     

Plant hormesis and Shelford's tolerance law curve

Shelford's law of tolerance is illustrated by a bell-shaped curve depicting the relationship between environmental factor/factors' intensity and its favorability for species or populations.It is a fundamental basis of ecology when considering the regularities of environment impacts on living systems,and applies in plant biology,agriculture and forestry to manage resistance to environmental limiting factors and to enhance productivity.In recent years,the concept of hormesis has been increasingly used to study the dose-response relationships in living organisms of different complexities,including plants.This requires the need for an analysis of the relationships between the hormetic dose-response model and the classical understanding of plant reactions to environments in terms of Shelford's law of tolerance.This paper analyses various dimensions of the relationships between the hormetic model and Shelford's tolerance law curve under the influence of natural environmental factors on plants,which are limiting for plants both in deficiency and excess.The analysis has shown that Shelford's curve and hormetic model do not contradict but instead complement each other.The hormetic response of plants is localized in the stress zone of the Shelford's curve when adaptive mechanisms are disabled within the ecological optimum.At the same time,in a species range,the ecological optimum is the most favorable combination of all or at least the most important environmental factors,each of which usually deviates slightly from its optimal value.Adaptive mechanisms cannot be completely disabled in the optimum,and hormesis covers optimum and stress zones.Hormesis can modify the plant tolerance range to environmental factors by preconditioning and makes limits of plant tolerance to environmental factors flexible to a certain extent.In turn,as a result of tolerance range evolution,quantitative characteristics of hormesis(width and magnitude of hormetic zone) as well as the range of stimulating doses,may significantly differ in various plant species and even populations and intra-population groups,including plants at different development stages.Using hormetic preconditioning for managing plant resistance to environmental limiting factors provides an important perspective for increasing the productivity of woody plants in forestry.     

Flood tolerance of four tropical tree species

Many seasonally flooded habitats in the tropics are dominated by one or a few tree species. We tested the hypothesis that the inability to tolerate flooding restricts most species from becoming established in flood-prone habitats. We compared morphological and physiological responses to flooding in seedlings of Prioria copaifera Griseb., a species that forms monodominant stands in seasonally flooded habitats, and in three species confined to flood-free sites; namely, Calophyllum longifolium Willd., Virola surinamensis Aubl. and Gustavia superba (H.B.K.) Berg. Flooding reduced photosynthesis at Day 45 in all species by 10-30%. By Day 90, photosynthesis returned to the control rate in Prioria, but not in the other species. Flooding reduced stomatal conductance by 25-35% in all species except Calophyllum, and it reduced leaf area growth by 44% in Virola, but not in the other species. All species survived 90 days of flooding without mortality, leaf chlorosis, leaf necrosis, or leaf abscission. Flooding reduced root:shoot ratio significantly in Gustavia and Calophyllum, but not in the other species, and it reduced maximum root depth by 29% in Prioria, but by 61% or more in the species from flood-free habitats.     

A study on the shade tolerance ofMuehlewbeckia complera

Muehlewbeckia complera was introduced to China in 2002 as indoor-hanging ornamental foliage plant. The experiment of the shade tolerance for this species was carried out in different light intensities (0.14–946.00 μmol·m⁻²·s⁻¹). After 40 days in experimental areas, leaf photosynthentic characteristics indexes ofM. complera in different photosynthesis active radiation (PAR) were measured with LI-COR6400 apparatus, such as the light compensation point, light saturation point, and maximum net photosynthesis rate, at the same time, the increments of total leaf area and leaf amount were measured. The results showed that the optimum light intensity range forM. complera was from 9.26 μmol·m⁻²·s⁻¹ to 569.00 μmol·m⁻²·s⁻¹ (463–28150 lx, relative humidity (RH) for 46–60%, temperature at 16–22°C). Under this condition, leaf photosynthetic efficiency was tiptop. AlthoughM. complera belonged to the moderate sun-adaptation plant species, the plant growth was inhibited when PAR increased to the level of 569.000 μmol·m⁻²·s⁻¹ or above.M. complera could sprout new leaves in photosynthesis active radiation of 0.16–19.22 μmol·m⁻²·s⁻¹ (8–961 lx), or 10 μmol·m⁻²·s⁻¹ for above 6 h. Foundation item: This study was supported by the Research Foundation of Northeast Forestry University. Biography: YUE Hua (1962-), female, Associate professor in Northeast Forestry University, Harbin 150040, P. R. China. Responsible editor: Zhu Hong     

Tree-growth analyses to estimate tree species' drought tolerance

Climate change is challenging forestry management and practices. Among other things, tree species with the ability to cope with more extreme climate conditions have to be identified. However, while environmental factors may severely limit tree growth or even cause tree death, assessing a tree species' potential for surviving future aggravated environmental conditions is rather demanding. The aim of this study was to find a tree-ring-based method suitable for identifying very drought-tolerant species, particularly potential substitute species for Scots pine (Pinus sylvestris L.) in Valais. In this inner-Alpine valley, Scots pine used to be the dominating species for dry forests, but today it suffers from high drought-induced mortality. We investigate the growth response of two native tree species, Scots pine and European larch (Larix decidua Mill.), and two non-native species, black pine (Pinus nigra Arnold) and Douglas fir (Pseudotsuga menziesii Mirb. var. menziesii), to drought. This involved analysing how the radial increment of these species responded to increasing water shortage (abandonment of irrigation) and to increasingly frequent drought years. Black pine and Douglas fir are able to cope with drought better than Scots pine and larch, as they show relatively high radial growth even after irrigation has been stopped and a plastic growth response to drought years. European larch does not seem to be able to cope with these dry conditions as it lacks the ability to recover from drought years. The analysis of trees' short-term response to extreme climate events seems to be the most promising and suitable method for detecting how tolerant a tree species is towards drought. However, combining all the methods used in this study provides a complete picture of how water shortage could limit species.