Factors and mechanisms influencing seed germination in a wetland plant sawgrass

Abstract

Sawgrass (Cladium jamaicense) is the predominant plant and vegetation community in the Florida Everglades. Germination of sawgrass seeds in the laboratory or nursery has been difficult and problematic, yet little is known about the physiological mechanistic regulation of the sawgrass seed germination process. In the present study, we examined the factors and mechanisms that influence sawgrass seed germination. We found that removal of seed husk and bracts, pre-soaking with bleach (hypochlorite), breaking the seed coat, or combinations of these treatments promoted the rate and success of germination, whereas presence of seedencasing structures or treatment with husk/bract extract inhibited germination. We further detected the presence of abscisic acid (ABA) in the husk and bract. Experiments with ABA and gibberellin biosynthesis inhibitors fluridone and tetcyclacis suggested that ABA already presented in the pre-imbibed seeds, and not derived through post-dormancy de novo synthesis, contributed to the inhibition of seed germination. Examination of bleach and mechanical treatments indicated the physical barrier presented by the seed-encasing structures provided additional mechanism for the long-term delay of seed germination. Based on the results of this study and others, we discussed the implications of sawgrass seed dormancy and germination in relation to its natural habitat and proposed a hypothesis that the protracted seed dormancy in sawgrass offered an adaptive advantage in the pre-anthropogenic Everglades environment, but may become a liability in the current man-managed Everglades water system.

Allelopathic Activity of Dehulled Rice and its Allelochemicals on Weed Germination

“…Dehulled rice showed strong inhibitory effects on root length of lettuce and shoot height of radish while hulls and rice exhibited stimulatory effects. It is believed that dehulled rice seeds have faster speed and higher percentage of germination than intact rice seeds do [29,30]. Hulls play a pivotal role in dormancy of rice seeds [27].…”

“…Hulls play a pivotal role in dormancy of rice seeds [27]. Husk or seed coat may restrict the commencement of seed germination in two mechanisms, preventing the water absorption and releasing inhibitory hormones (abscisic acid) to procrastinate germination [30]. Dehulling is one of the dormancy breaking methods to activate and boost seed germination [31].…”

Continuous biosynthesis of abscisic acid (ABA) may be required for maintaining dormancy of isolated embryos and intact seeds of Euonymus alatus

“…The fact that ABA promoted the dormancy of E. alatus embryos demonstrates that they are responsive to the ABA signal, and if these embryos contain an appropriate level of ABA, they will remain dormant. Fluridone, an inhibitor of carotenoid biosynthesis has been widely used to block ABA production in higher plants and to demonstrate the role of ABA in seed dormancy and germination, and other growth and developmental processes (Webb et al 2009). Since fluridone effect on carotenoid biosynthesis appears to be specific, the inhibitor provides a powerful tool to study the roles of ABA in various physiological or developmental events, particularly seed dormancy (Kucera et al 2005;Li and Walton 1987).…”

“…Since fluridone effect on carotenoid biosynthesis appears to be specific, the inhibitor provides a powerful tool to study the roles of ABA in various physiological or developmental events, particularly seed dormancy (Kucera et al 2005;Li and Walton 1987). Fluridone blocks phytoene desaturase, which is a critical enzyme in the formation of the ABA precursor carotene (Li and Walton 1990a, b;Walton and Li 1995;Webb et al 2009). Our data shows that embryo dormancy is enhanced by ABA but drastically reduced by fluridone.…”

Involvement of Arbuscular Mycorrhizal Symbiosis in the Distribution of Sawgrass and Cattail in Florida Everglades

“…It is known that sawgrass has a low rate of seed germination, slow population growth, low reproductive yield, and a long life cycle (Davis 1991;Miao and Sklar 1998;Webb et al 2009). On the other hand, cattail is an opportunistic species with high population growth and reproduction rates, long-distance seed dispersal, a short life cycle, and a high biomass turnover rate (Davis 1991;Newman et al 1996;Miao and DeBusk 1999;Miao 2004).…”