Effects of Storage and Burial on Germination Responses of Encapsulated and Naked Seeds of Turnipweed (Rapistrum rugosum) to Light

Abstract

Information on the germination and viability of turnipweed seeds could be helpful in developing appropriate management strategies for this weed. Therefore, experiments were conducted to investigate the effects of light, storage conditions, duration of storage or burial, and seed type (naked, i.e., fruit wall was removed and encapsulated in siliques) on germination and viability of turnipweed. The naked and encapsulated seeds (fruit) were kept under five different storage conditions, including dry storage at 25 ± 2 C and 3 ± 1 C and outdoor environments (soil depths of 10, 20, and 40 cm). All seeds were retrieved every 2 mo and tested for germination in light and darkness. At each exhumation date, nongerminated seeds were treated with triphenyltetrazolium chloride to test their viability. The germination of seeds liberated from siliques (85%) was markedly greater than that of seeds in intact siliques (20%). The germination response of naked and encapsulated seeds to light varied between storage conditions and through time. Under indoor conditions (room and cold), both seed types had greater germination percentages in dark on most occasions than those in light. On the contrary, the germination of siliques buried at soil depths of 20 or 40 cm was considerably stimulated by light. Under indoor conditions, the percent viability of both seed types only declined marginally, whereas seeds buried in soil showed high rates of mortality. Seeds in intact siliques persisted longer under either indoor or outdoor conditions than naked seeds.

Delayed dehiscence of the pericarp: role in germination and retention of viability of seeds of two cold desert annual Brassicaceae species

“…A similar result was found in the Brassicaceae species R. raphanistrum (Cousens et al 2010), D. strictus (Lu et al 2010) and I. violascens (Zhou et al 2015). One way in which the pericarp can inhibit germination is via mechanical resistance (Cousens et al 2010;Lu et al 2010;Ohadi et al 2011;Mamut et al 2014). That is, the embryo does not have enough growth potential to overcome the mechanical resistance of the pericarp and other covering layers (endosperm, seed coat) until the seeds become non-dormant.…”

“…They may (i) protect seeds against predation by animals (Cousens et al 2010); (ii) prevent germination during unfavourable environmental conditions for seedling survival (Cousens et al 2010;Lu et al 2010;Ohadi et al 2011); (iii) provide an internal environment that keeps the seed moist after a period of moderate rainfall (Mamut et al 2014;Zhou et al 2015), thus extending the effective period over which germination can occur, or enabling a germinating seedling to survive until the next rainfall event through slowing desiccation (Cousens et al 2010;Mamut et al 2014); and/or (iv) inhibit germination and spread the timing of germination of seeds in a given cohort over several years (Lu et al 2015b), which may be a bet-hedging strategy. In L. filifolium and N. korolkovii, opening of the pericarp only after the fruits have been wet for a few days helps ensure that there is adequate soil moisture for seedling establishment at the time seeds germinate.…”

“…The fruit, rather than the seed, is the dispersal/germination unit in many angiosperms, including quite a few species of Brassicaceae (Maun & Payne 1989;Liu & Tan 2007;Cousens et al 2010;Lu et al 2010Lu et al , 2015aOhadi et al 2011;Mamut et al 2014). Plants of Brassicaceae species produce siliques (dry two-valved capsule, three or more times longer than wide) or silicles (dry two-valved capsule, less than three times longer than wide), which differ in structure and size (Hall et al 2011;Zhou et al 2001).…”

Seed dormancy in six cold desert Brassicaceae species with indehiscent fruits

“…3; Lu et al, unpublished data). In Rapistrum rugosum, Ohadi et al (2011) reported that dormancy was caused by the pericarp, but Cousens et al (1994) concluded that dormancy in distal seeds (in the fruit of this species) may also, at least in part, be due to the seed coat and/ or embryo. 2), suggesting that the embryo lacked enough growth potential (push power) to overcome the mechanical Table 3.…”

“…The Brassicaceae includes many species with dry dehiscent as well as those with dry indehiscent fruits, and previous research on the effect of the pericarp on germination reveals that it may prevent germination in this family (Mekenian and Willemsen, 1975;Cheam, 1986;Cousens et al, 2010;Lu et al, 2010;Ohadi et al, 2011;Mamut et al, 2014). To understand the germination ecology of species with such fruits, the role of the pericarp in delaying and/or promoting germination must be considered.…”