Changes in the cellular content of polyamines in different tissues of seed and fruit of a normal and a hull-less seed variety of pumpkin during development


Comparative analyses of cellular contents of free polyamines (putrescine, spermidine, spermine) in different tissues of developing fruit and seed of a normal and hull-less seed mutant of pumpkin (Cucurbita pepo L.) were undertaken on different days post anthesis (dpa). The hull-less condition affects hemicellulose, cellulose, and lignin contents of secondary cell walls of the seed coat (testa) tissue resulting in a thin papery testa. Polyamine analyses of the pericarp and the testa tissues showed a higher level of all three polyamines early in development coincident with the period of rapid cell division, differentiation, and growth. All three polyamines declined in the testa upon maturity. The hull-less testa had higher levels of all three polyamines compared to the normal testa, which could be either due to a decrease in conjugation of free polyamines with phenolic acids as a result of their reduced production for lignin biosynthesis, and/or in relation to reduced water stress in the hull-less testa. The embryo, which had the highest polyamine levels of all tissues, showed a greater increase in putrescine with time in the normal seed as compared to the mutant seed. It is suggested that this may be due to the reduced level of stress in the mutant seed as the testa retains higher moisture level for a longer time. Both spermidine and spermine showed a gradual decline with the development of the embryo. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.

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Plant Science



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© 2003 Elsevier Science Ireland Ltd.