Abstract
Polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM) are implicated in plants’ responses under conditions of abiotic stress. Previous research in other crops has indicated that polyamines and changes in their concentrations are associated with drought tolerance under conditions of water-deficit stress; however, no information exists on cotton (Gossypium hirsutum L.). Growth chamber experiments were conducted with two cotton cultivars differing in drought tolerance, ST5288B2F (drought-sensitive) and Siokra L23 (drought-tolerant) in order to investigate the distribution of free polyamines, the effect of water-deficit stress on the polyamine metabolism of cotton reproductive units and their subtending leaves as well as the possible relationship between polyamines and drought tolerance in cotton. Our results showed that cotton ovaries contained significantly higher levels of total free polyamines compared to their subtending leaves under both control and water stress conditions. Water-deficit stress significantly increased PUT concentrations in ST5288B2F, while SPM levels significantly decreased in Siokra L23. The results indicated that water-deficit stress significantly affected cotton polyamine metabolism in reproductive structures and their subtending leaves; however, no clear relationship between drought-tolerance and changes in polyamine accumulation was established. Further research is needed to elucidate the mechanism according to which water-deficit stress affects polyamine metabolism.
Highlights
Polyamines (PA) are organic compounds, highly charged and found in bacteria, plants and animals
The results of our study showed that cotton free polyamine concentrations vary depending on the type of tissue
Variations in polyamine concentrations have been reported depending on the species, the organ as well as the type of tissue analyzed [16] with the general trend being that increased polyamine concentrations occur inreproductive units compared to vegetative tissues [1]
Summary
Polyamines (PA) are organic compounds, highly charged and found in bacteria, plants and animals. PAs occur in free forms, conjugated with phenolic acids forms or bound to other low molecular weight compounds or macromolecules forms, and are implicated in a variety of plant functions, that include photosynthesis and stomatal conductance, enzyme activation and maintenance, cell division and differentiation, morphogenesis and embryogenesis as well as organogenesis ([1] [2] and references therein). The role of PAs in reproductive development appears to be more than mere participation due to the significant increase in their concentrations as plants transition from their vegetative to reproductive stage of growth ([2] and references therein). Flower induction includes PA participation [1] along with flower initiation, pollination, fruit growth and ripening while sexual differentiation of tissues is reported to be strongly dependent on PA biosynthesis and catabolism. Post-fertilization development has been reported to be regulated by PAs and numerous reports on PA and their role in stimulating fruit set and fruit development exist ([2] and references therein)
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