Relationship between water content and afterripening in red rice

Abstract

Reactions regulating seed dormancy can proceed at water contents which are probably too low to permit metabolic activity. The loss of dormancy via afterripening of red rice. (Oryza sativa L.) seeds was examined as a representative case. Equilibration of seeds to various moisture contents showed that afterripening was most rapid at 6–14% moisture content (dry weight basis). Afterripening did not occur at > 18% moisture content and was severely inhibited at < 5% moisture content. Seed viability was greater than 95% for all treatments. Utilization of moisture isotherms to calculate water‐binding enthalpy values identified the optimal afterripening range as approximately the boundary between water‐binding region 1 and region 2. From these findings, it is suggested that afterripening may involve some oxidative reactions which are inhibited at lower water contents by the rising free‐energy and at the higher side by metabolic reactions.

Dormancy cycling in Arabidopsis seeds is controlled by seasonally distinct hormone-signaling pathways

“…Changes in AR50 in the autumn and spring occur when soil is moist (>20%) and seeds are therefore likely to be hydrated. This has significant ecological implications as it is widely considered that the release of dormancy via afterripening occurs in the dry state (14). Thus, in damp temperate soils, the rapid loss of dormancy occurring in hydrated seeds indicates that dry afterripening-traditionally considered to be the primary driving force for loss of dormancy (in both laboratory and field) (15-17)-may have a limited role during dormancy cycling in soil seed banks of temperate regions such as the United Kingdom.…”

Isolation of three dormancy QTLs as Mendelian factors in rice

“…Environmental conditions that facilitate afterripening vary by species. For example, rice normally requires afterripening under warm, dry conditions (Leopold et al, 1988) and Arabidopsis responds best to cool, moist conditions (Koornneef and Karssen, 1994). Rice species (Oryza ssp) differ in patterns of afterripening under warm, dry conditions (Veasey et al, 2004).…”

The Effects of Combinations of Temperature and Seed Moisture Treatments on Hardseededness in Okra

“…Leopold, Glenister and Cohn (1988) found that in red rice the best response to after ripening was obtained when seeds are treated between 6 and 14% at 22°C which belongs to water binding region of 1 and 2. That region of water isotherms is involved non-enzymatic oxidative reactions in seed (Priestley 1986).…”

“…Vertucci and Leopold (1984) found that there are three regions of water-binding the seed components and these help for interpretation of various biochemical processes which can occur in seeds as a function of water content. Region 1 and 2 involves nonenzymatic oxidation, while region 3 is identified as the uptake of oxygen with production of CO2 (Vertucci and Leopold 1986) Leopold, Glenister and Cohn (1988) showed that afterripening red rice occurred between 6 and 14% moisture content which includes parts of water -binding region 1 and 2. In okra, hardseededness as well as afterripening treatment efficiency is related to seed moisture.…”