Rafidain Journal of Science

Abstract

This study investigates the effects of root exudates of corn (Zea mays L.), sorghum (Sorghum bicolor subspecies tichnicum), sunflower (Helianthus annuus L.) ,Tomato (Lycoperscum esculentum L.), pepper (Capsicum frutescens L.),and okra (Hibiscus esculentus L.) on the growth of each others when they are planted in the same field at the same time by applying the stair step technique to study the interference among these plants species.
The results of the study revealed that the root exudates of the plants in question can be classified into three distinct groups: the first group reacted positively with the root exudates of the other plants; In other words their growth has been stimulated by the root exudates of other plants.
It has been noticed that the growth of tomato and sorghum plants has been stimulated significantly by the root exudates of okra plant. Also, the growth of both sorghum and pepper plant has been stimulated by the root exudates of sunflower and has reached 34 % for the sorghum plant.
The second group reacted negatively with the root exudates of other plants. In other words the growth of this group has been inhibited by the effects of root exudations. The growth of pepper plant has been significantly reduced by the root exudates of okra and sorghum plants, the reduction rate reached (29%, 37%) respectively. The growth of tomato and okra plants has been reduced by the root exudates of sunflower plant and the reduction has been 43% in dry weight of tomato plant, but it has not been significant in okra’s plant.
The third group has been affected neither positively nor negatively by root exudates of other plant, such as the growth of pepper plant that had not been affected by root exudates of sunflower.