Effect of priming on germinability and salt tolerance in seeds and seedlings of Physalis peruviana L

In some species, pre-germination treatments such as priming can increase germinability and the speed of the process, besides conferring tolerance to abiotic stress. The central effect of priming is the slow and controlled absorption of water in seed tissues, allowing the membranes to reorganize and synthesize protective substances against stress. This study was performed to assess the effects of priming on the invigoration of seeds and seedlings of Physalis peruviana subjected to salt stress. Seeds of P. peruviana were primed in polyethylene glycol 6000 to -0.8 MPa and were germinated in solutions with different salt concentrations (0, 4, 8 and 12 dS m-1). In addition to the rate of radical emergence, post-seminal development was also evaluated until the emergence of the cotyledons. Germinability decreased with increasing salt solution concentrations in both types of seeds. Priming appeared to alleviate the effects of salt stress in the early stages of development of P. peruviana. Total dry mass of seedlings increased under saline conditions, suggesting possible physiological adjustments induced by priming.Keywords: Germination, priming, salt stress, SolanaceaeAfrican Journal of Biotechnology, Vol 13(19), 1955-196

Alpha-Glucan, Water Dikinase 1 Affects Starch Metabolism and Storage Root Growth in Cassava (Manihot esculenta Crantz)

Abstarct Regulation of storage root development by source strength remains largely unknown. The cassava storage root delay (srd) T-DNA mutant postpones storage root development but manifests normal foliage growth as wild-type plants. The SRD gene was identified as an orthologue of α-glucan, water dikinase 1 (GWD1), whose expression is regulated under conditions of light/dark cycles in leaves and is associated with storage root development. The GWD1-RNAi cassava plants showed both retarded plant and storage root growth, as a result of starch excess phenotypes with reduced photosynthetic capacity and decreased levels of soluble saccharides in their leaves. These leaves contained starch granules having greatly increased amylose content and type C semi-crystalline structures with increased short chains that suggested storage starch. In storage roots of GWD1-RNAi lines, maltose content was dramatically decreased and starches with much lower phosphorylation levels showed a drastically reduced β-amylolytic rate. These results suggested that GWD1 regulates transient starch morphogenesis and storage root growth by decreasing photo-assimilation partitioning from the source to the sink and by starch mobilization in root crops