豹皮樟扦插苗对干旱胁迫的生理响应机制

Physiological response mechanism of Litsea coreana cutting seedlings to drought stress

【目的】探明干旱胁迫处理对豹皮樟扦插苗相关生物量及生理指标的影响,为制定其大田水分管理措施提供科学依据。【方法】采用盆栽控水,通过自然干旱的方法模拟干旱胁迫,以豹皮樟3年生扦插苗为研究对象,观察比较不同干旱胁迫处理扦插苗的相关生物量及生理指标的变化规律。【结果】土壤体积持水量与扦插苗的根系活力显著负相关,与春梢长度、春梢重量、根系干重和一级侧根数显著正相关,相关系数依次为-0.773、0.578、0.754、0.822和0.706。轻度干旱胁迫对豹皮樟春梢和根系生长无显著影响。处理组扦插苗的光合作用能力均较CK下降;中度和重度干旱胁迫的光合午休时间为11:00—13:00,较CK的光合午休时间提前;轻度干旱胁迫无明显午休现象,在13:00后光合作用能力增强。豹皮樟扦插苗通过降低氮代谢速率适应干旱逆境,扦插苗叶片中的可溶性糖和游离脯氨酸的含量与土壤体积含水量显著负相关,相关系数分别为-0.792和-0.832;可溶性糖含量在中度胁迫条件下最高(111.49%),Pro含量在重度胁迫条件下最高(0.249%),轻度胁迫条件下的可溶性糖含量和Pro含量与CK无显著差异。豹皮樟扦插苗叶片的SOD酶活性与叶绿素含量和MDA浓度显著正相关,相关系数分别为:0.697和0.712;POD酶活性与土壤体积持水量显著正相关,相关系数为0.778,Pro含量与土壤体积持水量显著负相关,相关系数为-0.832;豹皮樟扦插苗在轻度干旱胁迫条件下,光合和呼吸代谢变缓,SOD酶将O^(2-)·歧化成H_(2)O_(2)的能力下降,以降低叶片细胞中H_(2)O_(2)和MDA等有害物质的积累来适应逆境。【结论】豹皮樟扦插苗具有抗轻度干旱胁迫的能力。

[Objective]The effects of drought stress on related biomass and physiological indexes of Litsea coreana cutting seedlings were studied to provide the scientific basis for formulation of water management measures in field cultivation of L.coreana.[Method]The change law in related biomass and physiological indexes of L.coreana cutting seedlings with three years old cultured in pots was compared under different drought stress simulated by the natural drought method.[Result]The soil volumetric water-holding capacity was negatively related to roots activity of L.coreana cutting seedlings significantly and its correlation coefficient was-0.773.The soil volumetric water-holding capacity was positively related to spring shoot length,spring shoot weight,roots dry weight and first lateral root number of L.coreana cutting seedlings significantly and their correlation coefficients were 0.578,0.754,0.822 and 0.706 respectively.The mild drought stress had no significant effect on growth of spring shoots and roots of L.coreana cutting seedlings.The photosynthesis capacity of L.coreana cutting seedlings under different drought stress declined compared with CK.The photosynthetic noon break of L.coreana cutting seedlings under moderate and severe drought stress was at 11:00-13:00 and was earlier than CK.There was no photosynthetic noon break of L.coreana cutting seedlings under mild drought stress and the photosynthesis capacity strengthened after 13:00.The L.coreana cutting seedlings adapted the drought adversity by decreasing nitrogen metabolic rate.The soluble sugar and proline content in leaves of L.coreana cutting seedlings was negatively related to soil water-holding capacity significantly and their correlation coefficients were-0.792 and-0.832 separately.The leaf soluble sugar content reached the maximum(111.49%)under moderate drought stress and leaf proline content was up to the maximum(0.249%)under severe drought stress.There was no obvious difference in leaf soluble sugar and proline content between mild drought stress treatment and CK.The leaf SOD activity and chlorophyll content of L.coreana cutting seedlings were positively related to MDA concentration significantly and their correlation coefficients were 0.697 and 0.712 separately.The leaf POD activity was positively related to soil volumetric water-holding capacity significantly and its correlation coefficient was 0.778.The leaf Pro content was negatively related to soil volumetric water-holding capacity significantly and its correlation coefficient was-0.832.The L.coreana cutting seedlings under mild drought stress adapted the drought adversity by slowing down photosynthesis and respiratory metabolism and reducing accumulation of H_(2)O_(2)and MDA harmful substance in leaf cells due to decrease of SOD disproportionation ability from O^(2-)to H_(2)O_(2).[Conclusion]L.coreana cutting seedlings have the ability to resist mild drought stress.