PHYSIOLOGICAL AND ANATOMICAL STUDIES ON DROUGHT TOLERANCE OF PEA PLANTS BY APPLICATION OF SOME NATURAL EXTRACTS

Two pot experiments were conducted at the Faculty of Agric. Minufiya Univ., during the winter seasons of 2005/2006 and 2006/2007 to investigate the effect of water stress and its combination with natural extracts (garlic, yeast and eucalyptus) as foliar spray on growth, physiological aspects and chemical composition, anatomical structure as well as yield and its components of pea plants. The obtained results indicated that, all studied characters of growth, relative water content (RWC), total water content (TWC), free water content (FWC), transpiration quotient (TQ) and leaf water potential (LWP), photosynthetic pigments, total soluble sugars (TSS), minerals (N, P and K) contents in leaves, anatomical structure of stem as well as yield and its components were negatively affects by low water supplies, while the reverse effect was obtained in osmotic potential (OP), bound water content (BWC), leaf water deficit (LWD), membrane integrity (Ml), water use efficiency (WUE), peroxidase and phenoloxidase activity, total carbohydrates (TC) and proline concentration. The application of natural extracts significantly increased in most tested parameters compared with control plants. The interactive effect of drought stress and the usage of natural substances increased significantly growth parameters, RWC, FWC, TWC, TQ, LWP, photosynthetic pigments, N, P and K content in leaves, the different tissue areas of stem as well as yield and its components except No. of pods/plant and No. of seeds/pod, moreover Improve in OP, BWC, WUE, enzymes activity, Ml, TC and proline concentration compared with untreated plants. High level of water stress (W2) caused a highly significant reduction in the ground tissue, conductive tissue and total stem area. Pea plants grown under low water stress treatment (Wi) with the application of garlic extract showed highest values of ground tissue, conductive tissue and total stem area. Foliar spray of pea plants with natural extracts increased significantly weight of pods/plant, number and weight of seeds/plant and weight of 100 seeds compared with untreated plants. Best results were obtained by foliar spraying with garlic extract under Wi treatment for weight of seeds/plant and weight of 100 seeds. It could be recommended that, application of natural extracts led to overcome the deleterious effect of drought and consequently, resulted in high yield of pea plants. In this respect, garlic extract showed superiority over yeast or eucalyptus.