Researches Of Physiological And Ecological Characteristics Of Aloe Vera Irrigated With Seawater

The variations of ecological characteristics, soil salinity, phytochroms, polysaccharide, soluble sugars, pralines, malondialdehyde (MDA), membrane stability, inorganic cations, and antioxidant enzyme activities in Aloe vera L. irrigated with seawater having varying salinity were studied. Moreover, experiments including parameters above were conducted in two aloe (Aloe vera L.) cultivars (F0₀ and F6₅₀) to assess the capability of salt-tolerance. Besides, variations of two cultivars in cell structures and molecular level were also observed.The results indicate seawater concentration has no effect on absorbency, pH, relative density, dry matter and water contents in Aloe vera leaves. While, seawater stress causes increased MDA and membrane penetration, decreased phytochroms, prolines and NO₃^--N. It is beneficial to plant growth when irrigation was done with 10% seawater, because of higher ratio of K⁺/Na⁺ and lower ratio of Na⁺/Ca²⁺. In addition, the polysaccharide contents in Aloe vera leaves increase twice and triplication under 25% and 50% seawater irrigation respectively, the barbaloin contents increase over triplication in var. 75% seawater and over twice in var. 50% seawater and var. 100% seawater. However, when seawater concentration exceeds 25% the growth of plant was inhibited, biomass decreased, flowering time was deferred, Ca²⁺ content decreased caused by Na⁺ accumulation in leaves. Besides, superoxide dismutase (SOD: EC 1.15.1.1) activity maintain relative stability as a whole, peroxidase (POD: EC 1.11.1.7) activity increased significantly at 10% seawater level, whereas decreased at higher seawater levels, and catalase (CAT: EC 1.11.1.6) activity decreased with increasing seawater. But, Aloe vera L. can decrease soil salinity when seawater concentration under 75%.Moreover, there are higher biomass, phytochroms, soluble sugars (especially other soluble sugars except of glucose and sucrose) and antioxidant enzymes activities in F6₅₀ than that in F0₀ when irrigation was done with 60% seawater. In addition, F6₅₀ had a relative superiority in growth under salinity conditions due to higher chl a/chl, car/chl and K⁺/Na⁺ ratios and lower Na⁺/Ca²⁺ ratio than F0₀. Under seawater stress, inorganic cations accumulations in root and stem instead of organic solute accumulation in leaf and decreases in CAT and POD in F6₅₀ suggest that the osmotic adjustment of Aloe vera is main depend on accumulating inorganic cations in root and stem other than small molecule organic solute. Though there are no difference between F0₀ and F6₅₀, electron microscope observation showed more differences between them and F6₅₀ cell are more orderly and compact after generational cultivation. The growth superiority of F6₅₀ is due to its physiological adjustment against seawater stress.