水体泥沙对苦草生长发育和叶片光合生理特性的影响

Influence of silts on growth and development of Vallisneria Asiatica and its leaves' photosynthetic physiological characteristics in Turbid Water

用粒径小于100μm的泥沙分别配置浊度为30、60、90NTU和120NTU的浑浊水体,将苦草(Vallisneria asiatica)幼苗分别种植于上述水体中,水深约60cm,定期统计植株的叶长、叶宽、叶片数和株数,利用水下饱和脉冲荧光仪(DIVING～PAM)测定泥沙附着苦草叶片在光化光下的荧光参数,并测定其超氧化物歧化酶和过氧化物酶活性。结果表明,随着水体中泥沙含量的增加苦草植株的叶宽、叶片数和植株数呈显著的降低趋势,在浊度30NTU的水体中,植株叶长增长速度显著大于对照;随着实验时间的延长,在泥沙含量较高的水体(浊度≥60NTU)中,植株逐渐死亡,而在浊度30NTU的水体中,幼苗能进行正常的生长发育。秋季植株开花时,叶片上的泥沙附着量逐渐增大,在30NTU水体中泥沙附着叶片的实际光化学效率、光化学荧光淬灭系数和电子传递速率均显著高于对照,而且附着叶片的超氧化物歧化酶和过氧化物酶活性与对照的差异不显著。表明在低浓度泥沙水体中泥沙附着有利于苦草叶片PSⅡ免受秋季高光照的伤害,从而减缓苦草叶片光合功能的衰减。因此,在泥沙含量较低的浅水体(浊度≤30NTU)中可以适当引种苦草幼苗(最好由冬芽和根状茎萌发得到),植株能正常生长发育和繁殖。

Seedlings of Vallisneria asiatica （SVA） were planted in the waters with turbidity of 30NTU, 60NTU, 90NTU or 120NTU. The turbidity of the water was controlled by sand particles smaller than 100μm in diameter, and the effect of water turbidity on the growth of SVA was examined. The photosynthetic fluorescence characteristics of the leaves attached on silts was determined in situ by a developed, submersible, pulse-amplitude modulated （PAM） fluorometer, diving-PAM in actinic irradiance. The activities of superoxide and peroxide of the leaves were also determined. The experimental results indicated that the stains number and leaf numbers, and leaf width of SVA decreased significantly as the turbidity of water increased after exposing the seedlings in turbid water for 60 days. However, the leafs grew faster in the water with turbidity of 30NTU than that in the control water. With the extension of experimental time, the plants gradually died in turbid water with high silts content （turbidity ≥ 60 NTU）. In contrast, seedlings can grow and develop normally in the turbid water with a turbidity of 30 NTU. The silts amount attached on leaves increased gradually with bloom of the plants in autumn. The effective quantum yield of photosystem II, photochemical quenching and electron transport rate of leaves attached on silts determined in the turbid water of 30NTU were higher than those measured in the control water. However, the activities of superoxide and peroxide of the leafs did not show a significant difference by comparison with the control syetem. It was shown that silt attachment could avoid damage from high irradiance in autumn to photosynthetic system II of the leaves at low turbidity of water, consequently maintain photosynthetic capacity of the leaves. Therefore, seedlings of V. asiatica might be adapted to low turbid shallow water of silts （turbidity ≤ 30 NTU）,and normally grow and develop, and breed. It is also suggested that the best seedlings were germinated from winter buds or rhizome of V. Asiatica..