干旱-复水处理对杠柳幼苗光合作用及活性氧代谢的影响

采用人工控制土壤水分试验，以80%田间持水量处理为对照，研究了3次干旱-复水处理对2年生杠柳幼苗叶片光合作用,根、茎、叶膜脂过氧化和抗氧化系统的影响.结果表明: 在干旱条件下, 杠柳叶片相对含水量和光合速率(P_n)显著降低，光合色素含量升高. 干旱复水后，叶片相对含水量完全恢复，反映了杠柳较强的旱后修复能力；叶绿素含量和P_n均明显高于对照，表现出补偿效应，适度干旱诱导了杠柳的抗旱适应性.干旱胁迫使P_n下降,以气孔限制为主，但在中午发生了非气孔限制；幼叶、新茎和细根中的超氧阴离子产生速率升高，丙二醛含量则降低，说明这些幼嫩组织未受到氧化伤害.不同器官中SOD、CAT和POD活性及变化趋势不同，以细根的3种保护酶的反应最为灵敏，说明细根是杠柳适应干旱环境的重要器官.器官间的相互合作与协调使杠柳能有效地适应干湿交替的干旱环境.

Effects of drying and re-watering on the photosynthesis and active oxygen metabolism of Periploca sepium seedlings

Taking two-year old Periploca sepium seedlings as test materials, an experiment with controlled soil water contents was conducted to study the effects of repeated drying and re-watering on the leaf photosynthetic characteristicsand the lipid peroxidation and antioxidant system in young leaves, mature leaves, old leaves, new stems, and fine roots. The seedlings were subjected to three cycles of drying and re-watering, with regular irrigation to maintain the soil water content at around 80% of field capacity as the control (CK). Under drying,the leaf relative water content (RWC) and net photosynthesis rate (P_n) decreased significantly, while the leaf photosynthetic pigments content increased.When the seedlings were re-watered, their leaf RWC recovered to the CK level, showing a strong repair capacity after drying. Both the leaf chlorophyll contentand the P_n after repeated drying and re-watering presented a higher level than those of the CK, indicating a compensatory effect appeared and an appropriate drought stress being able to induce the adaptability of P. sepium to drought stress. Stomatal closure was the main factor limiting P. sepium photosynthesis under drought stress, while non-stomatal limitation only worked at noon. Under drying, the superoxide anion radical (O₂) production rate in young leaves, new stems, and fine roots increased while the malondialdehyde (MDA) contents decreased, suggesting that these young tissueswere not suffered from the oxidative stress. The activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in different organs had different variation trends, with those in fine roots changed actively, suggesting the important role of fine roots in the acclimation of P. sepium to drought environment. It was the cooperation and coordination among plant organs that made P.sepium more adaptive to the repeated drying and wetting conditions in drought -prone regions.