以科尔沁沙地生长的沙漠植物差不嘎蒿(Artimisia halodendron)、小叶锦鸡儿(Caragana microphylla)、扁蓄豆(Ruthenian medic)、胡枝子(Lespedeza bicolor)、黄柳(Salix gordejevii)和猪毛菜(Salsola collina)为材料,研究了自然状况下光合作用、保护酶活性及渗透调节物质含量的日变化特征及相关关系。结果表明:(1)5个C3植物光合作用日变化为中午降低类型,净光合速率(Pn)在10:00到达第1个高峰,在14:00出现第2个高峰,其中4个植物第2高峰平均Pn仅为第1高峰的37%。C4植物猪毛菜光合作用为单峰型。(2)在第1个Pn高峰期间,伴随着光合有效辐射(PAR)增高6.5倍和气温(Ta)增高,叶片水分亏缺度(VPD)增加3~6倍、气孔导度(Gs)下降60%;叶片丙二醛(MDA)含量增加18%,Pn增加3~13倍;过氧化物酶(POD)活性(除了扁蓄豆)平均增高29%、过氧化氢酶(CAT)活性(除胡枝子)平均增加82%;叶片可溶性糖含量增加48%,脯氨酸含量(除差不嘎蒿)增加74%。(3)午间和午后在大气PAR和Ta较高、叶片VPD较大、MDA含量和Pn下降时,渗调节物含量和抗氧化酶活性仍维持较高水平。日间叶片光合特性与保护酶活性和渗透调节物质含量的日变化间具有一定的相关性。抗氧化酶(尤其是POD和CAT)和渗透调节物(脯氨酸和可溶性糖)不仅在Pn增加过程中维护细胞氧自由基代谢和水分代谢平衡,而且在Pn较低时抑制膜脂过氧化和维持水分平衡,因此它们在日间提高Pn和恢复叶片光合作用上起重要的生理保护作用。6种植物参与抗逆生理调节的抗氧化酶和渗透调节物种类上差异显著。
The daily changes in photosynthetic characteristics, antioxidant enzyme activities and osmoregulation substance contents were investigated in response to daily variation of radiation in six desert palnts, Caragana microphylla, Salsola collina, Ruthenian medic, Lespedeza bicolor, Salix gordejevii, and Salsola collina in the Horqin Sandy Land, Inner Mongolia, China to understand how correlation of photosynthetic characteristics was with antioxidant enzyme activities and osmoregulation substance contents. The results obtained are as followes:(1).The diurnal changes of photosynthestic rate of five C3 desert plants belong to noon-sescent type. The first net photosynthetic rate(Pn) was peaked at 10:00am, second one was at 14:00pm which was only 37% of first Pn in four C3 desert plants(C.microphylia, R.medic, L.bicolor, S.gordejevii). While Salsola collina(C4) was unimodal type.(2) During reaching first peak of Pn, with rising up of radiation(PAR)and air temperature(Ta) from 6:00 am, vapor pressure dificit(VPD) increased by 3-6 times, stomata condition(Gs) decreased by 60%, as same times contents of malondialdehyde(MDA) and soluble sugar and proline(exception A.halodendron) increased by 18%, 48% and 74%; the activities of peroxidase(POD)(exception R.mecid) and CAT(exception L. bicolor) raised by 29% and 82%; Pn increased by 3-13 times among the six plants.(3) During the noon and after noon, when PAR and Ta were higher,Pn decreasing was accompanied with increasing of Gs and VPD, and the leaves still hold higher in contents of proline and soluble sugar and stronger in activities of antioxidant enzyme. It suggested that diurnal photosynthetic characteristics was correlated with antioxidant enzyme activities and osmoregulation substance contents. Antioxidant enzyme(specialy POD and CAT)and osmoregulation substance(proline and soluble sugar)not only preserved metabolism balance of active oxygen free radicals and water and in physiological protective fuction for the photosynthese of desert plants when Pn rised, but also played physiogical regulation role in recovering of photosnthese and cell normal metabolism. But six desert plants have different antioxidant enzymes and osmoregulation substances involved in adpting to desert environment.
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