Showing papers in "Seed Science and Technology in 2018"

Contributions of photosynthetic organs to the seed yield of hybrid rice: the effects of gibberellin application examined by carbon isotope technology

Abstract: Changes in the structure and quality of a hybrid combination population have been observed after the application of gibberellins. Such changes would affect the accumulation and distribution of photosynthetic products, which would subsequently affect the yield during hybrid rice seed production. In this study, photosynthetic physiological characteristics and the distribution of photosynthetic products were evaluated in a field experiment. The transport of panicle photosynthetic products to grain was demonstrated using a 14C isotope tracer technique. The contribution ratios of the panicle and leaf to yield in the hybrid rice seed production were 32.3 and 42.1%, respectively. Through isotope tracing technology, it was determined that about 90% of the photosynthetic products of the panicle and 50% of those of the leaf were delivered to the panicle. During the filling period, the contribution of panicle to yield was concentrated in the early period (0–10 days after pollination), and the contribution of leaf to yield was more significant in the late period (10 days after pollination to maturity). These results suggest that the panicle makes an important photosynthetic contribution (equivalent to that of the flag leaf) during the process of grain filling, especially at 0–5 days after the heading stage.

Impacts of priming on seed germination and seedling emergence of Cleistogenes songorica under drought stress

Abstract: Cleistogenes songorica is an important native grass in northern China mainly used for regeneration of degraded land and in the grass-livestock industry. However, it is sensitive to drought stress during germination and early growth stages. Seed priming is a good approach to enhance germination and seedling establishment under stress conditions. Laboratory, greenhouse and field experiments were conducted to investigate the role of hydropriming, osmopriming and spermidine priming in enhancing germination, emergence and drought tolerance of C. songorica. Drought stress led to decreased germination and emergence, poor seedling growth, higher levels of lipid peroxidation and reactive oxygen species (ROS) accumulation. However, all seed priming treatments assuaged the detrimental effects of drought stress. Such improvements were associated with lower lipid peroxidation and generation of ROS (H2O2 content), and greater antioxidant enzyme activity in primed seeds under drought. Furthermore, an increase in the nuclear DNA contents of seeds from 2C to 4C occurred during priming, indicating progression from the G(1) to G(2) phase of cell cycle, the positive effect of priming was closely related to the percentage of cells at the G(2) stage of the cell cycle and to the G(2)/G(1), ratio.

High-temperature drying of seeds of wild Oryza species intended for long-term storage

Abstract: Freshly harvested seeds of four accessions of different wild Oryza species belonging to the AA genome (Oryza sativa complex) were initially dried at 15% RH and either 15, 30, 45 or 60°C for a week before final drying at 15% RH and 15°C. Subsequent storage experiments at 10.9% moisture content and 45°C showed seed longevity increasing as the initial drying temperature increased up to 45°C. A subsequent decrease in seed longevity was observed for seeds dried at 60°C. Thus, similar to cultivated rice, these results suggest that initial drying of wild Oryza species seeds at 45°C is advantageous for long-term storage compared with drying directly at 15% RH and 15°C.

Ethanol exposure can inhibit red spruce ( Picea rubens ) seed germination

Abstract: Flotation of seeds in solvents is a common means of separating unfilled and filled seeds. While a few protocols for processing red spruce (Picea rubens) seeds recommend ethanol flotation, delayed and reduced germination have been reported. We conducted an ethanol bioassay on seeds previously stored at -20°C to quantify the concentration required to separate red spruce seeds and the effects on germination. We used seeds from Canada (CAN) that had been exposed to ethanol during processing, and seeds from the United States (USA) that had not been exposed to ethanol during processing. Seeds were exposed to 10 ethanol concentrations (10-100%) and deionised water was used as a control. The effective concentration of ethanol for 50% (EC50) of the seeds to sink ranged by source from 70.9 to 90.7%, with all seeds sinking in 100% ethanol. The use of less than 100% ethanol is not adequate for seed separation, as some filled seeds could float and be mistakenly categorised as unfilled. The mean EC50 of ethanol that inhibits germination was significantly higher for USA sources (52.7%), than for CAN sources (40.8%; P < 0.05). Ethanol concentrations that inhibited germination coincided with delays in germination. The mechanism of phytotoxity was not determined; however, damage during extraction, desiccation and storage at -20°C are potential sources. We recommend separating red spruce seeds by physical means rather than ethanol flotation to avoid potential negative impacts on germination.

Comparison of seed desiccation sensitivity amongst Castanea sativa, Quercus ilex and Q. cerris

Abstract: The distribution and propagation by seed of species with recalcitrant seed storage behaviour requires knowledge of the lowest safe moisture content before desiccation damages seed survival. These values were comparatively high and varied amongst the forest tree species Castanea sativa (58%), Quercus cerris (40-47.5%) and Quercus ilex (44%) (Fagaceae) collected at one site in one year. Relations between lower seed moisture contents and viability (radicle emergence) were sigmoidal and quantified by logistic curves, with Q. ilex showing the smallest seed-to-seed variation.

Longevity of 285 seed lots of wheat in hermetic storage compared with independent estimates from the seed viability equation

Abstract: The longevity in hermetic storage at 40°C with 14.1-15.7% moisture content of 285 seed lots of wheat (Triticum aestivum L., cv. Tybalt), harvested at or before maturity from control or modified environments under rain shelter or after simulated rainfall in three consecutive years (2010-12), was compared with independent estimates from the seed viability equation and previously-published viability constant values for wheat. Around half of the observations provided good agreement with these independent estimates of longevity, but some of the seed lots harvested close to maturity in 2012, or before the end of the seed-filling phase in 2011, survived longer in storage than prior estimates.