PJB-2000-25
FECUNDITY, SEED CHARACTERISTICS AND FACTORS REGULATING GERMINATION OF RHYNCHOSIA MINIMA (L.) D.C.
S. SHAHID SHAUKAT AND NAZIA BURHAN
Abstract
Fecundity of three Rhynchosia minima populations was compared. The old-field population exhibited highest fecundity as well as average reproductive output weight, followed by the population existing in a vacant lot while the population in a natural undisturbed shrub-dominated community showed lowest fecundity and average output weight. Variation in seed weight within and between populations was demonstrated. The implications of seed size variation are discussed. Seeds have water impermeable seed coats and thus they have physical dormancy. Physical scarification with sand paper was more effective in breaking seed dormancy than chemical scarification with hydrochloric acid. Dry heat treatment (50oand 70oC) markedly increased the germination percentage. Under field conditions dry heat during summer apparently breaks seed dormancy thereby allowing the seeds to germinate in considerable numbers after rain showers. Greater germination percentage was observed in light compared to dark. Final germination percentage varied with temperature (25o- 40oC) with the optimum at 35o. Significant inhibition of germination occurred at 6, 7, and 8 bar NaCI salinity, while in polyethylene glycol (PEG 4000) germination was reduced at 7 and 8 bar. At iso-osmotic concentrations PEG 4000 caused lesser inhibitory effect compared to NaCI salinity.
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