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SEED PHYSIOLOGY, PRODUCTION & TECHNOLOGY

Conjugated and Free Polyamine Levels in Normal and Aborting Maize Kernels

Dep. of Agronomy, National Taiwan Univ., Taipei, Taiwan 106, Republic of China

* Corresponding author (lurhs{at}ms.cc.ntu.edu.tw)

Kernel abortion in maize (Zea mays L.) can cause significant reductions in yield. Abortion usually commences early in development and frequently occurs because of stresses such as water deficit or low light. Polyamines have been implicated in development processes of fruits and seeds, but in maize the changes of polyamine levels during kernel growth are still unclear. The objectives of this study were to investigate the roles of polyamines in the early stages of kernel growth and kernel abortion. Two single-cross hybrids with different kernel abortion characteristics were grown in a greenhouse with shade treatment. During early development of normal, naturally aborting, and shade-induced aborting kernels, temporal changes in the concentrations of endogenous putrescine (PUT), spermidine (SPD) and spermine (SPM) and their free, perchloric acid (PCA)-soluble conjugated, and PCA-insoluble bound forms, were measured. Changes in DNA content and the number of endosperm nuclei were also measured. Total polyamine levels in normal kernels rapidly increased 4 to 6 d after pollination (DAP), and peaked during active endosperm cell division. The most abundant polyamines were, in order, PCA-soluble conjugated PUT, PCA-soluble conjugated SPD, and free PUT. Aborting kernels had significantly lower levels of polyamines than normal kernels after 4 DAP. The low polyamine levels were temporally associated with a low number of endosperm nuclei and low DNA content. The results suggest that polyamines may be involved in the regulation of early endosperm development in maize.

Abbreviations: ABA, abscisic acid • ACC, 1-aminocyclopropane-1-carboxylic acid • DAP, days after pollination • IAA, indoleacetic acid • PCA, perchloric acid • PUT, putrescine • SPD, spermidine • SPM, spermine