PUTRESCINE EXTENDS EFFECTIVE POLLINATION PERIOD IN COMICE PEAR (PYRUS-COMMUNIS L) IRRESPECTIVE OF POSTANTHESIS ETHYLENE LEVELS

Putrescine (PUT) 10(-3) M, a polyamine applied at bloom, enhanced pollen tube ovule penetration and delayed ovule senescence, extending the effective pollination period of cultivar 'Comice' pear (Pyrus communis L.) by at least 2 days and 4 days in 1985 and 1986, respectively, without reducing post-pollination flower ethylene levels. Evolved flower ethylene peaked at pollination and again at petal senescence in vivo while vacuum-extracted ethylene peaked only during fertilization. Endogenous polyamine levels were not related to ethylene levels during the post-bloom period in any flowers. After pollination, putrescine-treated flowers exhibited lower levels of evolving ethylene than untreated flowers. Hand-pollinated flowers had greater polyamine levels than unpollinated. Putrescine-treated flowers had lower endogenous polyamine levels and higher nitrogen contents than untreated flowers. Earlier pollen tube penetration, delayed ovule longevity and extended 'Comice' effective pollination period from a PUT application were not associated with reduced post-anthesis, ethylene levels.