低温胁迫时间对4种幼苗生理生化及光合特性的影响

以盐肤木(Rhus chinensis)、假连翘(Duranta repens)、老鸭嘴(Thunbergia erecta)和葛藤(Pueraria lobata)4种幼苗为试验材料,研究了人工模拟下的低温胁迫环境(6℃)对幼苗叶片生理生化及光合特性的影响.结果表明:(1)随低温胁迫的延长,假连翘幼苗的叶绿素含量先升后降,其余3种幼苗持续下降,低温解除后均显著回升；4种幼苗的脯氨酸含量持续上升或波动；葛藤幼苗的可溶性蛋白质含量先升后降,其余幼苗显著上升,且低温解除后有所增加；4种幼苗叶片可溶性糖含量以及丙二醛含量呈增加趋势,SOD活性持续上升或先升后降.低温解除后,盐肤木幼苗的SOD活性略有上升,其余幼苗显著下降.(2)随低温胁迫的延长,4种幼苗的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)均持续下降,假连翘的胞间CO2浓度(Ci)持续上升,其余幼苗先降后升.低温解除后4种幼苗叶片Pn、G、Tr均有不同程度的回升,Ci有不同程度的下降.低温胁迫和恢复48 h期间,4种幼苗的脯氨酸、可溶性糖、可溶性蛋白质含量的增加和SOD活性的稳定或增加,减轻了幼苗叶片细胞的膜脂过氧化程度,维持了细胞膜的完整性,是幼苗对低温胁迫适应性反应的重要调节机制.恢复48 h时的Pn、Gs和Tr均有不同程度的回升,Ci有不同程度的下降,说明4种幼苗有一定的抗寒能力.(3)用主成分分析法分别对生理生化指标和光合生理指标进行分析,均得出4种幼苗的抗寒性顺序为葛藤＞盐肤木＞老鸭嘴＞假连翘,这一结果可为采矿石废弃地生态恢复的植物筛选提供科学依据.

Effects of low temperature stress on physiological-biochemical indexes and photosynthetic characteristics of seedlings of four plant species

Low temperature stress is one of the major environmental factors affecting the process of physiology and photosynthesis of plants, which is known to cause many physiological and biochemical changes in plant metabolism such as protein denaturation, lipid liquefaction, the increased activity of antioxidant enzymes or perturbation of membrane integrity. Also low temperature decreases capacity and efficiency of photosynthesis. Therefore, the above physiological and biochemical indexes and photosynthetic characteristics are often used as an indicator of stress injury in plants. In response to low temperature stress, plants naturally have developed diverse mechanisms which can mitigate the effect of stress and lead to the adjustment of plant tolerance. Effects of low temperature stress on physiological-biochemical indexes and photosynthetic characteristics were studied in the seedlings of Rhus chinensis, Duranta repens, Thunbergia erecta and Pueraria lobata. Results showed that (1) with increasing time of low temperature, the chlorophyll content of D. repens seedlings increased initially and then decreased, whereas that of the other three seedling types continuously decreased, and it rebounded significantly after removal of low-temperature stress for the four seedling types. The free proline content of the four seedling types gradually increased or fluctuated; the soluble protein content of P. lobata seedlings increased followed by an decrease, whereas the other three seedling types continuously increased, and that of the seedling types except for P. lobata rebounded significantly after low-temperature stress relieving; the contents of soluble sugar and MDA of the four seedling types tended to increase, their SOD activity continuously rose or rose initially and then fell, and SOD activity of the seedling types except for R. chinensis declined significantly after low-temperature stress relieving. (2) With increasing low temperature time, the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) continuously decreased for the four seedling types, and the intercellular CO₂ concentration (C_i) of D. repens continuously increased, whereas that of the other seedling types decreased followed by an increase. The P_n, G_s and T_r of the four seedling types increased to some extent, whereas their C_i decreased to some extent after low-temperature stress relieving. Increase in contents of free proline, soluble protein and soluble protein and increase or stead in SOD activity for the four seedling types alleviated degree of membrane lipid peroxidation of seedling cells and protected cell membrane, which is important regulatory mechanism of seedlings to low temperature stress. (3) The physiological indexes and photosynthetic indexes of the four seedling types were evaluated using principal component analysis, indicating that their ability of low temperature resistance was P. lobata > R. chinensis > T. erecta > D. repens. During low temperature stress and low-temperature stress relieving, osmotic substance content and SOD activity kept steady or increased in the seedlings of four plant species, and their P_n, G_s and Tr increased to some extent and C_i increased to some extent after low-temperature stress relieving, indicating that they had some ability of low temperature resistance. This result could supply scientific basis for plant selection in restoration of abandoned quarries.