Reproductive‐Resource Allocation in Rhizoma Peanut

Abstract

Partitioning of energy reserves between sexual (flower and seed) and asexual (rhizome) reproduction in rhizoma peanut (Arachis glabrata Benth.), a perennial, tropical‐forage legume, appears to be affected by environmental stress. If so, seed production may be enhanced by manipulating the growing environment. To investigate this possibility, the effect of defoliation frequency on the energy‐allocation balance of sexual vs. asexual reproduction of rhizoma peanut was determined. Four defoliation frequencies (nondefoliated, weekly, every 4 wk, and every 8 wk) were imposed on ‘Florigraze’ rhizoma peanut. Aboveground and rhizome biomass were sampled prior to treatment initiation (6 June 1988 and 15 June 1989) and every 4 wk until frost (24 wk in 1988 and 16 wk in 1989). During the first 8 wk, aboveground biomass of the non‐defoliated treatment nearly doubled. Concurrently, aboveground biomass of all defoliated treatments remained the same or declined. Rhizome biomass of all treatments declined during the same period but in most cases, recovered by the latter part of the growing season. Generally, aboveground biomass ranked (P < 0.05) 1 wk < 4 wk ≤ 8 wk < nondefoliated, and rhizome biomass ranked (P < 0.05) 1 wk = 4 wk = 8 wk < nondefoliated. Flowering was synchronous for all treatments, but sexual reproductive effort constituted <0.5% of total‐plant biomass because seeds were never produced. Defoliation positively affected (P < 0.05) both flower dry matter (DM) production and sexual:asexual ratio with treatments generally ranked nondefoliated = 1 wk < 4 wk = 8 wk. This study indicates that the partitioning of energy to sexual or asexual reproduction in rhizoma peanut can be altered in response to stress.