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Abstract
Mumian (Bombax ceiba) is a deciduous tree that can grow in the dry-hot valley of southwestern China. However, natural regeneration of mumian is significantly inhibited by some factors such as high temperature that can accelerate seed deterioration. The objective of this study was to identify the change of seedling growth component(s) in response to seed aging at 45 °C either at low relative humidity (15%) or at high relative humidity (100%) for 0, 1, 2, 3, and 4 days. Germination assay results at 30 °C in darkness showed an interaction between relative humidity and aging duration. At high temperature and low relative humidity seedling growth, weight of used seed reserve and fraction of seed reserve depletion significantly decreased with increasing of aging duration. But the conversion efficiency of mobilized reserve to seedling tissues did not change significantly. In contrast, at high temperature and high relative humidity, seedling growth and conversion efficiency of seed reserve utilization decreased significantly, but weight of used seed reserve and fraction of seed reserve depletion did not change significantly until seeds were dead. It was concluded that there existed a different pattern of seed reserve utilization for seeds aged at low and high relative humidity, and humidification of seeds at 45 °C for 1 day is a possible way to increase germination of mumian.
Seed deterioration is expressed as the loss of quality, viability, and vigor during aging. Several comprehensive reviews have identified free radical-mediated lipid peroxidation, enzyme inactivation or protein degradation, disruption of cellular membranes, and damage to genetic (nucleic acids) integrity as major causes of seed deterioration (McDonald, 1999; Walters, 1998). The rate of deterioration is determined by seed moisture, storage temperature, and seed traits that are influenced by genetic and environmental interactions during seed maturation and harvest (Walters et al., 2010). Among these factors temperature and seed moisture content and relative humidity are well studied (Ellis et al., 1992). Accelerated aging provides a simple method for studying the mechanisms of deterioration over short periods, and it generally is done by subjecting seeds to elevated temperature and high relative humidity (Kapoor et al., 2011). Aging is evidenced by delayed germination and emergence, slower growth, increased susceptibility to stress, and finally a decline in germinability compared with...