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Monday, February 2, 2015 at 12:20pm to 1:10pm
Peter Davies, professor, Plant Biology and Horticulture Sections, School of Integrative Plant Science, Cornell University
Horticulture Section seminar series. Also available via Polycom to A134 Barton Hall in Geneva.
Starting with Molisch  I will trace the ideas and research as to why monocarpic annual plants senesce and die, and the mechanisms behind these processes. Senescence usually follows flowering and can be delayed or prevented by the removal of flowers. In dioecious Spincea (spinach) even male flowers (with no seeds) trigger the senescence of the plant. The genetic line of peas G2, in which senescence is photoperiod dependent in the presence of two dominant genes, proved to be a way of examining changes that were related to senescence. There was a debate over whether the induction of senescence was dependent on a redistribution of nutrients to the fruits, or a senescence factor emanating from the fruits. There proved to be no physiological chemical basis for a senescence factor . A distribution of photosynthate occurs to the reproductive tissues at the expense of further vegetative growth occurs very early in the reproductive phase [3,4]. This is related to hormonal changes in the vegetative and reproductive tissues . In spinach even male flowers are large photosynthate sinks . However this nutrient redistribution is not solely a redistribution of carbohydrates, as leaves retain high levels of carbohydrates; nitrogen and minerals are more likely possibilities . Other changes, such as the suppression of lateral bud growth are needed for monocarpic senescence . The whole process is under genetic control that is now being elucidated.
1. Molisch, H. (1938) The longevity of plants (Der Lebensdauer der Pflanze). New York: E.H.Fulling. 226pp
2. Hamilton DA, Davies PJ (1988) Sucrose and malic acid as the compounds exported to the apical bud of pea following 14CO2 labeling of the fruit. No evidence for a senescence factor. Plant Physiol 88: 466-472.
3. Kelly MO, Davies PJ (1988) Photoperiodic and genetic control of carbon partitioning in peas and its relationship to apical senescence. Plant Physiol 86: 978-982.
4. Kelly MO, Davies PJ (1988) The control of whole plant senescence. Crit Rev Plant Sci 7: 139-173.
5. Zhu Y-X, Davies PJ (1997) The control of apical bud growth and senescence by auxin and gibberellin in genetic lines of peas. Plant Physiol 113: 631-637.
6. Sklensky DE, Davies PJ (2011) Resource partitioning to male and female flowers of Spinacia oleracea L. in relation to whole-plant monocarpic senescence. J Exp Bot 62: 4323-4336.
7. Davies P, Gan S (2012) Towards an integrated view of monocarpic plant senescence. Russian Journal of Plant Physiology 59: 467-478.