Study On The Photosynthetic Characteristics And The Drought Resistant Identification Of Elytrigia Desv

Elytrigia Desv, the perennial grasses of Gramineae, are the ideal plant materials for setting up artificial grasslands, for improving natural pastures, for protecting slopes and for conserving water and soils. However, the utilization values of Elytrigia species vary with their drought resistances that are relevant to their photosynthetic characteristics and other physiological properties. This study is to identify their drought resistances with related parameters.Experiments have been conducted with 4 Elytrigia species, i.e. E.elongata (Host) Nevski, E.repens (L) Nevski, E.intermedia (Host) Nevski, and E. trichophora (Link) Nevski. A LI-6400 portable photosynthesis analyzer (made in the USA) was used as instrument for a rapid method to determine diurnal changes of photosynthesis in the individual healthy leaves. The diurnal changes of physiological parameters inclosing net photosynthesis rate, transpiration rate and stomatal conductance, as well as the main factors affecting the net photosynthesis rate have been analyzed. Furthermore, 17 germplasm and materials of E.intermedia (Host) Nevski and E.repens (L) Nevski from different eco-geographical regions of 9 countries were taken for identification of drought resistance through soil drought stress in a sunlight greenhouse. Drought resistances of these 17 materials have been comprehensively evaluated through the analysis of physiological and biochemical parameters of relative water content, cell membrane permeability, free proline content and malondaildehyde content in the leaves of these plants. The germplasm and materials of the involved plants are classified into 3 groups, i.e. strongly, moderately or weakly drought resistances, according to the variation rates of the related parameters. The main results are follows:1. Diurnal changes of net photosynthesis rates in the 4 species of Elytrigia show similarly double peak curves, which have midday depressions at noon.2. Photosynthetic available radiation, leaf temperature, intercellular CO₂ concentration and stomatal conductance are all factors affecting the net photosynthesis rate, among them the last one, the stomatal conductance, is the main factor for the above Elytrigia (except for E.repens).3. Drought resistances are evaluated with variation rates of related parameters through marking points, the 17 tested plant materials of E.intermedia (Host) Nevski and E.repens (L) Nevski at the seeding period are classified into 3 groups with strong, moderate or weak drought resistances. The strongly drought resistant materials include AJ-2, Greenar, AJC-320,Reliant and 1 the moderately drought resistant materials include Slate, 2, Clarke, D-2111, Slate, DT-3175, D-1483 and X93035;and the weakly drought resistant materials include D-1987, 699, D-939, D-3244 and AJC-297, respectively.4.Field experiment used random blocks experiment design by setting up man-made canopies.Under drought stress, the agricultural characters of 17 germplasm and materials are mensurated and analysed.According to field experiment, the results of two identification methods are consistent.