Soluble Sugars and MDA in Leaves of Two ManilkaraSpecies under Salt Stress

Mechanism of the salt tolerance of Manilkara roxburghiana(Wight)Dubard and Manilkara zapota(L.)van Royen was investigated.The potted plants of the two species were watered with 0,2‰,4‰,6‰ or 8‰ NaCl solutions to observe the damages to the seedlings,as well as the induced changes on soil salinity and on the soluble sugars and MDA in the plant leaves by the salt stress.M.roxburghiana and M.zapota showed a Grade II salt damage under 3.38‰ and 2.88‰ NaCl stress,respectively,and a Grade III damage under 4.28‰ and 4.05‰ salt stress,respectively.The soluble sugars in the leaves of the plants increased with increasing concentration of NaCl,and were significantly different from those of Control without the salt stress.It was speculated that,with respect to the cellular osmosis,the soluble sugars might have increased by the plant in response to the presence of salt so as to improve its tolerance to the stress.The contents of MDA also differed significantly from Control under 6‰ or 8‰NaCl stress indicating the presence of a serious membrane lipid peroxidation on the plants.