Allelopathic effect of aqueous leaf extracts of selected trees on germination and seedling growth of rice

Aim : The present investigation aimed to study the allelopathic effects of aqueous leaf extracts of Emblica officinalis, Inga dulcis, Alstonia scholaris, Syzygium cuminis, Madhuca indica and Azadirachta indica trees on germination and seedling growth of rice. Methodology : The studies on germination and seedling growth was conducted in a BOD incubator. The number of seeds germinated daily was counted to study speed of germination, germination energy and number of days to 50% germination. DMSOwas used to extract the chlorophyll and carotenoid pigments of leaves. The chlorophyll and carotenoid contents were estimated by measuring the optical density through UV-VIS spectrophotometer. Relative watercontent of leaves was determined by soaking of leaves in waterfollowed by oven drying. Results : The effect of leaf extracts (5 and 10%) of Emblica officinalis, Inga dulcis, Alstonia scholaris, Syzygium cuminis, Madhuca indica and Azadirachta indica was studied on two rice cultivars viz. NK-5251 (Hybrid) and Gontra Bidhan-2 (high yielding variety). The experimental findings revealed that leaf extracts of different trees had significant effect on the germination and seedling growth of rice. The leaf extract of most of the trees, except Madhuca indica, reduced germination, chlorophyll content and RWC at higher concentration. The aqueous extracts of Madhuca indica significantly increased germination, seedling vigour, seedling dry weight,germination energy, speed of germination, chlorophyll content and RWC as compared to control. However, 5% extract of Madhuca indica recorded the highest germination percentage, seedling vigour, speed of germination, germination energy, seedling dry weight, chlorophyll content and RWC among all the treatments. Interpretation : The leaf extract of Emblica officinalis, Inga dulcis, Alstonia scholaris, Syzygium cuminis and Azadirachta indica plants at higher concentration reduced germination and early seedling growth of rice. The leaf extract of Madhuca indica plant, however, enhanced the performance. The positive allelopathic effect of Madhuca indica leaf extract may be attributed to the presence of phytohormones and biostimulants.