水分胁迫下木薯(NZ199)苗期生理响应分析

Physiological Response of Cassava(NZ199)at Seedling Stage under Water Stress

【目的】旨在研究不同水分胁迫对木薯幼苗生长、光合参数、叶片酶活性与扫描电镜结果的影响,为湖南地区木薯种植的防灾减灾提供理论依据及生产指导。【方法】以木薯NZ199为试验材料,设计土壤含水量占田间最大持水量的50%~60%为对照(CK),并设置土壤含水量占田间最大持水量的20%~30%为干旱处理(D)、80%~90%为高湿处理(W),研究干旱与高湿处理下木薯幼苗的生长、光合参数、叶片酶活性及扫描电镜的不同响应情况。【结果】与CK相比,D、W处理的净光合速率(Pn)、胞间CO_(2)浓度(C_(i))、蒸腾速率(T_(r))、气孔导度(G_(s))下降明显,其中D处理较W处理下降情况更为明显;D、W处理下的丙二醛(MDA)活性均显著高于CK处理,其中,D处理较CK增加了24.37%,W处理较CK增加了32.13%,在复水处理后,W处理MDA活性下降至CK水平,D处理MDA活性有所下降但仍高于CK处理。D、W处理下的过氧化氢酶(CAT)活性较CK显著升高,复水后D处理CAT活性较复水前下降了32.01%,W处理下降了25.78%,但仍显著高于CK水平。超氧化物歧化酶(SOD)活性在D处理中最高,CK处理其次,W处理中最低,复水后D处理中的SOD活性显著下降,W处理复水前后SOD活性无明显差异。渗透调节物质脯氨酸(Pro)在D处理下产生积累,在W处理下显著减少,干旱条件下的Pro较CK高出48.58%,高湿条件下Pro较CK降低了36.63%,复水处理后D、W处理Pro含量恢复至CK水平。D处理下的叶片气孔数目少,气孔缩小甚至关闭,表面有较厚且密集的蜡质层,W处理下的气孔数目多,气孔张开程度大,叶片表面蜡质层较薄且蜡质层呈丝状分布较少。【结论】NZ199幼苗在干旱条件下的光合指标抑制情况比高湿条件更为明显,干旱和高湿条件都会造成各类酶活的积累效应,且干旱条件对植株造成的伤害在复水后无法完全恢复至正常水平,与高湿条件相比,干旱条件下的气孔数目少且气孔关闭,并覆盖有较厚蜡质层。

[Objective]This study aims to explore the effects of different water stress on the growth,photosynthetic parameters,leaf enzyme activity and SEM results of cassava seedlings,thus providing theoretical basis and production guidance for disaster prevention and mitigation of cassava cultivation in Hunan.[Method]This experiment was conducted with cassava NZ199 as the test material,and 50%-60%(CK)of soil moisture content of maximum field water holding capacity was designed as the control,and the soil moisture content of 20%-30%was set as drought treatment(D)and 80%-90%as high humidity treatment(W).The different responses of growth,photosynthetic parameters,leaf enzyme activities and scanning electron microscopy of cassava under drought and high humidity treatments were investigated.[Result]Compared with CK,the Net photosynthetic rate(Pn),intercellular CO_(2)concentration(C_(i)),transpiration rate(T_(r)),stomatal conductance(G_(s))decreased significantly in the D and W treatments,with the decrease being more pronounced in the D treatment compared with that of the W treatment.The malondialdehyde(MDA)activity under D and W treatments were significantly higher than that of CK treatment,with the increase by 24.37%and 32.13%,respectively;after rehydration treatment,MDA of W treatment decreased to the CK level,and MDA activity of D treatment decreased but was still higher than that of the CK treatment.The catalase(CAT)activity under D and W treatments was significantly higher than that of CK after rehydration,CAT activity in D treatment decreased by 32.01%and decreased by 25.78%in W treatment,but still significantly higher than CK level.The superoxide dismutase(SOD)activity was the highest in D treatment,followed by CK treatment and the lowest in W treatment,and decreased significantly in D treatment after rehydration.There was no significant difference in SOD activity before and after rehydration in W treatment.Accumulation of proline was produced under D treatment and significantly reduced under W treatment,Pro was 48.58%higher under D conditions and 36.63%lower under W conditions compared with CK.Pro activity of D and Wtreatments recovered to CK level after rehydration treatment.The number of leaf stomata under D treatment was low,and the morphology of stomata were narrowed or even closed,the surface was covered with thick waxy layer and dense tomentum,while the number of stomata under high humidity treatment was high,the morphology of stomata were opened to a large extent,and the waxy layer on the leaf surface was thinner and the tomentum was less distributed in filamentous form.[Conclusion]The inhibition of photosynthetic indexes was more pronounced in NZ199 seedlings under drought conditions than under high humidity conditions,and both drought and high humidity conditions caused accumulation effects of various enzymatic activities.The damage caused by drought conditions to the plants could not be fully restored to normal levels after rehydration,the number of stomata was less,the stomata under drought conditions were closed and covered with thicker waxy layer and tomentum than that under high humidity conditions.