Minimizing the Harmful Effects of Cadmium on Vegetative Growth, Leaf Anatomy, Yield and Physiological Characteristics of Soybean Plant [ Glycine max (L.) Merrill] by Foliar Spray with Active Yeast Extract or with Garlic Cloves Extract

摘要

Pot experiments were carried out during the two successive summer seasons of 2010 and 2011 in thegreenhouse of Crops Physiology Research Department, Field Crops Research Institute, Agricultural ResearchCenter, Giza, Egypt to investigate the effect of pollution with cadmium at concentrations of 50, 100 and 200ppm on vegetative growth, leaf anatomy, yield and certain physiological aspects of soybean 'Giza 35'. Inaddition, the use of natural extracts from active yeast (60ml/L.) and garlic cloves (30 ml/L.) for minimizing theharmful effects of environmental pollution caused by cadmium on vegetative and reproductive growth as well ason leaf anatomy and physiological behaviour of soybean was also investigated. The obtained results revealedthat all assigned concentrations of cadmium induced significant decrease in all investigated morphologicalcharacters of vegetative growth (plant height, number of branches and leaves/plant, total leaf area /plant andshoot dry weight/plant) and in all studied yield characters (number of pods and seeds/plant, specific seed weightand seed yield/plant) of soybean 'Giza 35'. Moreover, the significant decrease in morphological and yieldcharacters got higher as the concentration of cadmium increased in irrigation water. Worthy to note that,soybean plants grown under stress of pollution with different levels of cadmium and sprayed with either yeast orgarlic extract had better growth behavior and yield than those of unsprayed with natural extracts. Likewise, theconcentrations of photosynthetic pigments (Chl. a, Chl. b and carotenoids), total sugars and phytohormonesfrom IAA and GA3 in leaves of cadmium polluted soybean plants were decidedly lower than those of controlplants. In this respect, increasing cadmium concentration in irrigation water decreased gradually photosyntheticpigments, total sugars, IAA and GA3 . It was found that yeast as well as garlic extracts were able to minimizethe harmful effect of cadmium and improve the concentrations of photosynthetic pigments, total sugars, IAAand GA3 in leaves of cadmium polluted soybean plants. Also, the percentage of crude protein and total lipids inseeds of cadmium polluted soybean plants were decidedly lower than those in seeds of control plants andincreasing cadmium concentration in irrigation water decreased gradually the percentage of crude protein and oftotal lipids. It is clear that foliar application with yeast or garlic extract was sufficient for reducing the harmfuleffect of cadmium and improve the percentage of crude protein and of total lipids in seeds of cadmium pollutedsoybean plants. At the same time, the concentration of phytohormone ABA in leaves and of cadmium in leavesand seeds of soybean plants was increased due to cadmium treatments, and the application of yeast or garlicextract on soybean plants grown under stress of pollution with cadmium minimized the harmful effect of suchheavy metal on concentration of ABA in leaves and on cadmium accumulation in leaves and seeds of cadmiumpolluted soybean plants. Concerning the anatomical structure of leaflet blades, treatment with 100 ppmcadmium decreased the thickness of both midvein and lamina due to the decrease induced in thickness of bothpalisade and spongy tissues as well as in the dimensions and components of main midvein bundle. The meanvalues of number of xylem rows and vessels/midvein bundle as well as of vessel diameter in leaflets of stressedsoybean plants were decidedly lower than those of control. The application of yeast or garlic extract causedenhancement in leaflets structure of polluted plants and the best results were obtained from treatment with 60ml. active yeast extract/L. which caused recovery of the reduction occurred in most of the histological characterswhere their mean values reached or surpassed those of control.