Hardseededness and Germinability of Velvetleaf(Abutilon theophrasti)as Affected by Temperature and Moisture

Abstract

Velvetleaf(Abutilon theophrastiMedic. ♯4ABUTH) seeds were exposed to variable moisture and temperatures from 15 to 100 C. As temperature increased, the percent of permeable seeds increased. Soaking 1 h at 70 C reduced hard seeds from 99 to 15 percent. Increased available water increased the effect of temperature on reduction of hard seeds. Thus, immersion in hot water was more effective than dry or humid heat. High temperature acted within a few minutes to reduce hardseededness. Viability of hard seeds was reduced at temperatures above 70 C. Germination of permeable seeds was optimal at 24 to 30 C and declined above 35 C. Germination of permeable seeds decreased after pretreatments above 40 C. Temperature and duration of heat exposure were inversely related to germination inhibition. Recently harvested seeds (3-yr-old) remained hard under alternating 4 to 34 C but became permeable after drying at 34 C. Old seeds (15-yr) did not become permeable after drying.