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ABSTRACT
Autotoxic effects of hot pepper on seed germination and growth of itself and lettuce were examined. Root leachates of hot pepper significantly inhibited the germination and radicle length of hot pepper and lettuce and the inhibitory effects increased with concentration. The leachates affected germination and seedling growth of lettuce more than hot pepper. The inhibitory effects of hot pepper on lettuce were noticed throughout the experimental period and were highest between 51-60 days. The autotoxic potential of leaf extract and root leachates was higher than root and stem extracts.
Keywords: Autotoxic potential, CRETS, hot pepper, lettuce, plant part extracts, root leachates
INTRODUCTION
Allelopathy is widely reported in agro-ecosystems and silviculture (3,9,10) and is also implicated in exotic plant invasion, replant and soil sickness (2,7). The main reasons of allelopathy are : imbalance of nutrients, soil hardening, soil acidification and serious disease or insect infestations. Some plants exhibit their allelopathic potential by release of allelochemicals into their surroundings through leaching, root exudates, volatilization, and/or decomposition of plant parts (13). Allelochemicals are low molecular weight organic compounds that can accumulate in plants, soils and other organisms (11). These compounds vary in chemical composition, concentration and localization in plant tissues and vary from plant to plant, with changes in both biotic and abiotic conditions (8). Allelochemicals have either harmful or beneficial effects on other plants in the vicinity (9,11). Hot pepper is an important Solanaceae vegetable, whose allelopathic potential has recently attracted widespread interest. It is commonly cultivated in continuous cropping systems of monoculture in large areas in China. This has led to serious problems including poor plant growth, declining production, nutrient uptake disorders and promotion of soil-borne diseases (5). Autotoxicity has been documented in many plants and is believed to be involved in natural and agro-ecosystem (1,4,14,15). Besides, the allelopathic potential of plant parts and root leachates and the difference in growth periods of plants on physiological functions of other plants, is not well known. Therefore, this study was aimed to evaluate the changes in the allelopathic effects of root leachates from different growth periods and plant part extracts of hot pepper on lettuce seed germination and growth.
MATERIALS AND METHODS
Collection of root leachates and trapping system (CRETS)
Hot pepper and lettuce seeds...