Physiological adaptation of waxapple to waterlogging

Waxapple (Syzygium samarangense Men. et. Perry) plants receiving up to 40d of continuous flooding treatment showed no symptoms of physiological disorder, but the treatment resulted in early flowering. In this report, several physiological parameters of flooded plants are compared with those of nonflooded plants. Both control plants and 9-d-flooding-treated plants exhibited aerenchyma formation in the cortex tissue beginning 5 cm from the root tip. After 7d flooding treatment, the oxygen consumption rate of the root section was only 20% of that of the controls. Following flooding treatment, the roots showed an increase in alcohol dehydrogenase activity as well as an increase in three isozymes. However, malate dehydrogenase activity was decreased, and no significant change of NADP-malic enzyme activity was observed. There were no significant differences in levels of ethylene, 1-aminocyclopropane-1-carboxylic acid and 1-(malonylamino) cyclopropane-1-carboxylic acid in petiole and roots of flooded and non-flooded plants during the stage examined. It is inferred that the presence of aerenchyma in the root cortex allows a higher level of internal gas exchange, and thus, makes waxapple surprisingly flood tolerant. However, reduced root oxygen consumption rate may have limited root respiration rate and vegetative growth.     

动物适应的生理反应

概述了动物适应在时间、空间和功能上的生理反应,并对这些反应的作用进行了简要的分析。时间的尺度包括短期、长期和发育的生理反应；空间的适应则从体表、血液、细胞外液及细胞内部加以说明：功能水平的适应以行为、生理、生化和形态的变化给以解释。     

Physiological adaptation to aridity in the bushveld gerbil, Tatera leucogaster

Oxygen consumption, rectal temperature, thermal conductance, and evaporative water loss (EWL) were determined in resting captive Tatera leucogaster at ambient temperatures of between 14 and 38 °C. Basal metabolic rate (BMR) was 0.86 ml O₂. min⁻¹ (S.D.=0.15, n = 6), 45% of that expected for a rodent of the same body mass (106.2 g). Minimum wet thermal conductance was 0.21 ml O₂. min⁻¹, °C⁻¹ (S.D. = 0.01, n = 6), 113% of that expected for a mammal of the same body mass. Wet thermal conductance increased exponentially at temperatures greater than 32 °C. Mean rectal temperature was 35.3 °C below 35 °C (S.D. = 0.5, n = 6) and 39.3 (S.D. = 0.6, n = 5) at 38 °C. Mean resting EWL was 1.43 mg. min⁻¹ (S.D. = 0.14, n = 6) between 15 and 32 °C and increased dramatically at temperatures above 32 °C. Combining our data with data from the literature suggests that gerbils (Family Muridae; subfamily Gerbillinae) have, on average, low BMR and average minimum wet thermal conductance when compared to other rodents and other mammals, respectively, of the same body mass. Similarly, rodents (including gerbils) from arid habitats have, on average, lower rates of EWL when at rest below thermoneutrality than do other rodents of the same body mass from mesic habitats.     

Physiological adaptation of crop plants to flooding stress

When crop plants are subjected to soil waterlogging, or an anaerobic condition, their root and shoot systems respond differently. A variety of morphological and anatomical alterations develop in the root system. Reduction of the root respiration rate has been reported in both flooding-tolerant and intolerant species. Besides alcoholic fermentation, several diverse fermentative bypasses take place, which ameliorate the poisoning through excessive accumulation of specific metabolic intermediates. Root systems starved of oxygen are also poor providers of mineral nutrients for both themselves and the shoot systems. Stomatal closure and non-stomatal metabolic alterations are responsible for the reduction of leaf CO2 incorporation. Plant hormones are much involved in regulation of these physiological adaptations.     

Physiological adaptation of the heart to pathological overloading

Chronic overloading of the rat heart induces a cascade of adaptational events that compensate for the increase in work. At the myocardial level there are two types of adaptational mechanisms: qualitative, represented by the isomyosin changes leading to an improved efficiency; and quantitative, the hypertrophy. We present new approaches exploring possible adaptational changes at other levels within the myocardial cell. Studies of heart overload were performed either in young rats with experimental aortic stenosis or in humans with chronic compensatory hypertrophy. By means of double immunofluorescence labeling of isolated myocytes with anti-V1 and anti-V3 myosin immunoglobulins, we showed that the shift from high- to low-ATPase isomyosins occurs rapidly after aortic stenosis (2-3 days). Cardiac myocytes were shown to be poor in tubulin but a microtubule pattern was clearly visualized by an immunofluorescence approach. Their role in the onset of adaptational processes after aortic stenosis in not yet clear. On the other hand, we showed that in humans, contrary to small rodents, the adaptational process at the isomyosin level is very small or nonexistent.     

岩溶木本植物对干旱的生理生态适应

受全球气候变暖和季风气候影响,西南岩溶区年降水量及其在季节间的分配发生明显变化,无雨期频率和持续时间增加,且基岩风化严重,基质储水能力差,致使岩溶木本植物面临的季节性和地质性干旱加剧。该文通过参考相关文献分析结构性状和生理调节探讨岩溶木本植物如何适应地质性和季节性干旱。结果表明岩溶木本植物应对干旱的策略与其他干旱、半干旱区的植物大体一致,主要有抗旱和避旱两种策略:抗旱性植物一般具有比叶面积小、叶肉多汁、储水组织发达、细胞液浓度高等适应干旱的特征,可通过增加木材密度、增强木质部导管的抗栓塞性和提高水分利用效率以适应干旱; 避旱植物则可通过小而密的气孔和叶脉、发达的表皮毛、栅栏组织和维管束鞘等结构特征减少水分丧失,并可通过落叶、深根吸收深层水源和脱落酸(ABA)介导提早关闭气孔以适应干旱。虽然关于岩溶植物形态结构和生理调节对干旱适应机制的研究取得了一定进展,但仍然存在一些亟待解决的问题,例如:深入研究岩溶地区基岩水分状况及其对植物的贡献; 加强岩溶木本植物根系结构和生物量分配、树木构型及根际微生物与木本植物干旱适应的协同关系研究; 同时探索如何将岩溶植物生态适应研究成果应用于生产实践中,科学指导石漠化治理与生态修复。