Morphological and Physiological Studies on Nodule Formation in Leguminous Crops. : IX. Effects of the leaves clipping on nodule formation in Ladino clover (Trifolum repens L.)

Abstract

Studies were made to get information concerning the influences of cutting on nodule formation in Ladino clover. Particular attention was given to the inactivation on active nodule and reactivation on inactive nodule in treated host plants. The results are summarized as follows: (1) The increase in nodule number and in nodule weight accompanied with growing of host plants was inhibited by leaves clipping treatments. In this cases, the total duration of an inhibitive period was proportionately increased with an increase of clipping volumes. (2) The active nodules (red pigmented) were inactivated to the inactive nodules (green pigmented) by leaves clipping treatments, by the following method: The lacked region in leghemoglobin, bacteroid-shape bacteria and starch was formed on base in the bacteroid tissue of active nodules. These lacked regions continuously enlarged from base to top of bacteroid tissue accompanied with progress in the senescence. (3) The inactive nodules (green pigmented) produced by clipping treatments were again activated to active nodules (red pigmented) during a regeneration periods of host plants in the following ways. The coexistence region with leghemoglobin, bacteroid-shape bacteria and starch was formed on base of bacteroid tissue of inactive nodules, and it successively enlarged uperward of bacteroid tissue. The completion of recovery of inactive nodules was detected after 5-6 days of the coexistence region formation. (4) When the host plants were removed for a periods of 2-4 days into the dark condition, the active nodules were inactivated. In this experimental condition, the application of 10 % sucrose solution to the leaves of host plants prevented the inactivation of active nodules. And, when all the leaves and leaf stalks except one leaf stalk per plant were cut off, the active nodules were inactivated. In this condition, (the absorption of 10 % sucrose solution with the leaf stalk remaining prevented the inactivation of active nodules. These results suggested that the leaves clipping on host plants bring down the carbohydrate concentration in host plants which helps inducing inactivation of active nodules.