盐胁迫对空心莲子草生长和光合作用的影响

用NaCl浓度为0(对照)、50、100、150、200、250、300、350mmol/L处理空心莲子草Alternantheraphiloxeroides(Mart.)Griseb]。结果表明:盐胁迫下,植株鲜重、干重和根冠比都下降,含水量和肉质化程度先略高于对照,而后逐渐下降;根、茎和叶中Na 含量呈上升趋势,而K 含量呈下降趋势,且在同一浓度的盐处理下,叶的Na 和K 含量最高,茎的次之,根的最低;游离氨基酸(free amino acid,FAA)逐渐减少,脯氨酸(proline,Pro)含量先略低于对照,而后则急剧上升,可溶性糖含量(soluble sugar,SS)的变化正相反;净光合速率(net photosynthetic rate,Pn)、气孔导度(stomatal conductance,Gs)和蒸腾速率(transpirationrate,Tr)呈下降趋势,胞间CO2浓度(intercellular CO2concentration,Ci)呈上升趋势;膜稳定性呈下降趋势。因此,空心莲子草是一种盐生植物,且最适盐浓度较低;Na 主要积累在地上部的茎和叶中。推测它有可能向盐渍土壤蔓延。

Effects of Salt Stress on the Growth and the Photosynthesis in Alternanthera philoxeroides (Amaranthaceae)

Alternanthera philoxeroides was treated with NaCl of different concentrations(0,50,100,150,200,250,300 and 350 mmol/L).The results showed:(1)Under NaCl treatment,the fresh weight,the dry weight and the root/shoot ratio decreased.(2)Water content and the succulency degree of whole plant appeared to increase first and then gradually decline as salinity increased.(3)Na contents increased and K contents decreased in root,stem and leaf.Na and K contents in leaf were the highest under the same salinity,those in stem were next and those in root were the lowest.(4)FAA content gradually decreased.(5)Pro content appeared to decline first and then increase as salinity increased.(6)Soluble sugar changed in the opposite direction.(7)Pn,Gs and Tr decreased and Ci increased.The relative conductivity of leaves increased significantly.(8)The malondialdehyde(MDA)content declined at about NaCl 50 mmol/L but increased under at about NaCl 100-350 mmol/L.Those parameters indicated that A.philoxeroides was halophyte,but its salt tolerance was not strong and its NaCl optimal concentration lowed 100 mmol/L.Na mainly accumulated in stem and leaf of A.philoxeroide and it would probably spread to the salt soil.