Competition among Individual Plants in Crop Population : V. Top-root relative growth habit of the plant in case the nutrition level was changed in the mid course of the stage

Abstract

We tried to ascertain that how thc growth habits of plants would be altered where the nutrition levels of cultural solution were changed in the mid course of vegetative growth stage from the viewpoint of top-root relationships. Materials used were Lolium multiflorum LAM., Mammos italian B sp. and Mammos A sp. as erect type and weeping type respectively. The experiments were carried out in a green house, and water culture with Hewitt's solution was adopted (Treatment N-L: nutrition level was changed 10 ppm→ 10 ppm→ 10 ppm→ 50 ppm, Treatment N-N: nutrition level was changed 50 ppm→ 10 ppm→ 50 ppm→ l0 ppm). The results obtained were as follows; 1. There was no remarkable change in the pattern of increase in the total plant dry weight under circumstances where the nutrition levels were changcd in the mid course of the growth stage of the plant. In the later stage of growth the total plant dry weight, however, was larger under high nutrition level than under the low nutrition level. 2. The value of relative growth coefficient h (h=tan θ) was altered parallel with increase or decrease in nutrition level. 3. The value of T/R 3-D ratio's, however, was changed elastically parallel with the change in nutrition level. 4. Change in mean stem nos/root nos. ratio (S/R nos. ratio) over each period among successive samplings with advance of growth stage was the same as the pattern of the change in T/R 3-D ratio. 5. The value of the estimated root surface area by using the area meter (Hayashi denko AAM-5) in low nutrition level were larger than those in high nutrition level. The value in low planting density were always larger than those in high planting density, i.e. D(9) > D(6) > D(3), throughout the experimental period. 6. The top-root relationships, however, showed the elastic reaction in accordance with the change in nutrition levels. From the viewpoint of community structure, it was considered that the change of two dimensional plane S/R nos. ratio and three dimensional T/R 3-D ratio in accordance with the nutrition level seemed to have the influence, in the result, on the change in the value of relative growth coefficient (h = tan θ).