Sand Plant - Agropyron Stress Physiological Studies

In recent years, the vegetation was destroyed severely in north of China with population explosion. The quality of atmosphere in Beijing, the capital of China, was depressed seriously because of the sand storm. Ministry of Science and Technology decided to deal with this problem by building windbreak forest system, so some plants, which grew well in sand areas and defend people from the sand and the pollution, were selected to grow in sand areas.Some plants which have strong resistance to adversity should be researched,. Mongolian wheatgrass is a long-lived perennial grass of the genus Agropyron. It is well adapted to the cold, arid conditions of the great plains and its leaves are rich in nutrition, so it is wide ranged in arid and semi-arid area of north of China. Not only is it an important forage grass, but also has an important ecological and genetic value because of its drought-resistant, cold-resistant and barren-tolerant traits.This paper selected two different species of wheatgrasses to research In order to find out the damage and the responses of plants at different stress, some physiological indexes were determined. These results would provide some information to geneticist and breeder who coud make better used of Agropyron.The main results were described as follows:Firstly, this paper pointed out that effect of PEG(polyethylene glycols) on some indexes of wheatgrass seedlings. The content of relative water decreased dramatically, the osmoregulatory substance increased notably, including proline and the soluble sugar. The defensive enzymes activity increased at light stress and decreased at middle or severe stress, the membrane penetrability and the content of MDA(malondialdehyde) increased notably. From the change of these indexes, the paper concluded that the wheatgrass had strong drought resistance. The reasons of strong resistance had three aspects. (1)Wheatgrass could remove the active oxygen by heightening the activity of theenzymes and protect the plants from damage at light stress. (2)Wheatgrass could keep turgor pressure by osmoregulation and flexibility ofcells to maintain plants developing in drought stress, some osmregulatorysubstance, such as the proline and the soluble sugar, increased.(3) Wheatgrass could reduce water dissipation by shutting up stoma and let some leaves wither.Secondly, this paper studied the effect of different concentration NaCl on wheatgrass and pointed out that the wheatgrass could maintain well-balanced physiology at light salt stress, but at high salt stress, the membrane penetrability increased, fresh weight reduced, the development was restrained distinctly, and the osmoregulatory substance increased notably, at last the plants perished. From these results, this paper concluded that the wheatgrass had strong salt resistance. The reasons of strong salt resistance had three aspects:(1) Wheatgrass could reduce the potentiality penetration in cell by increasing the osmoregulatotory substance, so the plants could absorb more water by roots.(2) Wheatgrass could restrain the growth of upground of plants more than that of underground, so the plant could absorb more water and reduced transpiration.(3) Wheatgrass could control Na+ transport to upground by withholding Na+ in root which can keep the balance of ion of upground.Thirdly, this paper compared the different responses of plants to these twostresses, the change of the defensive enzyme activity and the rate of losing water of leaves was different at two different stresses. The rate of losing water of leaves at drought stress was more rapid than that at salt stress, the leaves would wither and the change of activity of enzymes notably at drought stress, these results showed that the damage to plants was result from the oxidation at drought stress. At salt stress, the content of relative water of leaves changed slightly as well as did the activity of enzymes, these results showed that the damage to plants was caused by poison of ion and lack of nutrition .