The Effect of Prevention of Flowering on the Vegetative Growth of Inoculated Pea Plants

Abstract

Ttie removat of the apical buds from tlie lop of inoculated pea ptants before ftowering caused the axillary buds of the stem leaves to develop and thus further to branch. The vegetative growth of the test plants continued to be luxuiijint wben litooming was delayed. Wtiite ttie control ptants formed seed.s and ripi-ned. tlie vegetative growth of the stem of Itie test ptants increased at nio.st eigtit-foUt during Ihe same time. A new, additionat red part grew at the same time in the root nodules, which had already partly become green. The new red part branched later so that the imusuatty large nodules appeared quite odd. The weight of the tiranehed, large nodules had at the same time increased on the average six-fold and the vegetatively grown test plants synthesized even eight times more nitrogen than did the control plants. The eoncentration of tegbacmoglobin in tbe nodules formed by tlie bacterial strain u.sed in tbe experiment was not inereased, but the absolute amount of the pigment was raised six-fold as a result of the increased nodule mass. While the vegetative growth was going on, oxidation of the tegliaemoglobin was delayed.Analyses of nitrogen and amino acids were made for both test and control planls. The totat length of the branches in the largest test plant was 32 m compared wUti the nnbranched control plant which wa.s 1.30 m.

THE EFFECTS OF FLOWERING AND FRUIT FORMATION ON THE SUPPLY OF PHOTOSYNTHETIC ASSIMILATES TO THE NODULES OF PISUM SATIVUM L. IN RELATION TO THE FIXATION OF NITROGEN

“…Nodule yield was also increased, as reported by Roponen and Virtanen (1968). Tbese results again sbow bow, under some circumstances, increased nitrogenase activity and increased accumulation of '*C-pbotosynthates may be correlated.…”

“…In long-term experiments in wbicb the effect of the continuous removal of flowers on nitrogenase activity during ageing of pea plants from 3 to 5 weeks was studied, there was a three-fold increase in nitrogenase activity and a ten-fold increase in accumulation of '*C-pbotosyntbates in the nodules of treated plants. Nodule yield was also increased, as reported by Roponen and Virtanen (1968). Tbese results again sbow bow, under some circumstances, increased nitrogenase activity and increased accumulation of '*C-pbotosynthates may be correlated.…”

The Effect of Source—Sink Manipulations on Nitrogen Fixation in Peas

“…The effects of partial defoliation or complete pod removal on vegetative growth and symbiotic N2 fixation in legumes have been studied previously (Wilson 1942, Roponen and Virtanen 1968, Lawn and Brun 1974, Huxley and Summerfield 1976. In general, defoliation reduces N^ flxation, and removal of reproductive structures promotes vegetative growth and accompanying Nj fixation.…”

Gas-exchange activity, carbohydrate status, and protein turnover in root nodule subpopulations of field pea (Pisum sativum L. cv. Century)

“…This explanation still allows for the observed increase Nodule subpopulations in pea 37 in nodule growth and activity when pods were systematically removed (Roponen and Virtanen, 1968), since this treatment made even more carbohydrates available. However, it appears that under unstressed growth conditions the availability of carbohydrate is well balanced within the plant so that onset of pod-filling will not result in reduced availability in the root nodules.…”