Experimental Modification of Plant Senescence.

Abstract

The termination of the life cycle of annual and biennial plants is sudden and complete. Entire fields of grains and other annual crops die sinmultaneously, often in the early part of the growing season. Neitlher the function nor the physiological basis for this senescence is understood.Plant senescence has received little attention since the publication of a small, perceptive book by Molisch (6)

Seed Production Affects Maternal Growth and Senescence in Arabidopsis

“…Interestingly, control mechanisms exerted by developing seeds over maternal growth and life span have been observed in plants (Murneek, 1926;Molisch, 1929;Noodén et al, 2003). In legumes such as soybean (Glycine max), for example, both reproductive growth and the onset of leaf senescence are under correlative control (Noodén and Penney, 2001) by developing seeds so that plants grow and live considerably longer when developing fruits are continuously removed (Leopold et al, 1959;Lindoo and Noodén, 1977). Such a pattern is readily found in monocarpic plants (i.e.…”

“…Mainly, two competing hypotheses have received the most attention in the past, one that invokes a simple source-sink relationship (Molisch, 1929) and one that invokes offspring-derived signals (Wilson, 1997). By far the most extensive research examining the causes of monocarpic senescence has been performed in legumes such as pea (Pisum sativum) and soybean (Leopold et al, 1959;Lindoo and Noodén, 1977;Noodén and Murray, 1982), but even in these species the debate has not been settled. A potential role of the hormones auxin and abscisic acid (ABA) in correlative control has been discussed (Tamas and Engels, 1981).…”

Programmed senescence of plant organs

“…This idea of exhaustive death' has been largely discredited since leaf senescence is triggered in many plants in the absence of nutrient mobilization to developing fruit (Leopold et al, 1959;Thomas and Stoddart, 1980). However, the association of leaf senescence with the transition from vegetative to reproductive development is widely accepted as being integral to the reproductive strategy of plants.…”

Physiological observations of maize (Zea mays L.) genotypes differing in source-sink ratios

“…Decreasing sink strength by reduction or removal of the sink has also been observed to delay leaf senescence in some species (Leopold et al, 1959;Leopold, 1961;Moss, 1962;Mondai et al, 1978;Patterson and Brun, 1980). Inhibition of leaf CER has been observed in small grains (Birecka and Dakic-Wlodkowska, 1963;King et al, 1967), vegetables (Claussen and Biller, 1977;Hall and Milthorpe, 1978), root crops, (Burt, 1964;Nosberger and Humphries, 1965), legumes (Crookston et al, 1974;Mondai et al, 1978), and maize (Kiesselbach, 1948;Moss, 1962).…”

“…Decreasing the sink demand (ability to import assimilates) by fruit removal or reduction in size has been observed to delay lea^ senescence (Leopold et al, 1959;Leopold, 1961;Moss, 1962) and inhibit photosyn thesis in several species (Kiesselbach, 1948;Burt, 1964;King et al, 1967;Mondai et al, 1978). Decreasing the source by shading or removal of the leaves has also been shown to delay leaf senescence (Hopkinson, 1966;Hodgkinson, 1974) and increase photosynthesis (Allison and Watson, 1966;Wareing et al, 1968).…”