Senescence retardation

The four categories of plant responses will undoubtedly show increased PGR use in the future, yet it appears that propagation and plant height control may afford the most ready outlet for new commercial PGR products. Senescence retardation and morphological manipulation present real challenges for basic exploratory and developmental research and promise new product potential in the distant future. Economic potential will be recognized easily with imaginative use, even with the compounds presently available. 

CKs stand out as the most important class of senescence-retarding hormones [21, 27]. While CKs may function in a wide range of tissues, they may not be universal anti-senescence hormones, for other hormones, particularly auxin and the GAs, sometimes may retard senescence instead of, or together with, CKs [18]. 

McFarland, G. A. and Holliday, R. (1994). Retardation of senescence in cultured human diploid fibroblasts by carnosine. Exp. Cell Res. 212,167-175. 

In some studies, retardants have been implicated in yield enhancement mediated by the manipulation of crop canopy structure and the removal of dominance characteristics, leading to a more uniform crop and potentially higher yields. Senescence may be delayed. Although the maintenance of green tissue is a clear advantage with respect to yield production, prolonged seasons can expose the crop to damaging episodes of adverse weather and counteract the potential benefits of PGR treatment. 

Many investigators are seeking further improvements in the handling of fresh produce. Among methods receiving much attention are the use of postharvest chemicals, retardants of senescence, thermal treatment, controlled atmospheres, new packaging techniques, better temperature control in storage and transit, and irradiation. One method may work well with one fruit or a particular variety of fruit but not with another fruit. 

Freshness and retardation of color changes associated with senescence are benefits of the treatment (183, 184). Gibberellic acid applied after harvest was also reported to reduce decay of lemons (183), but its primary effect is to retain chlorophyll (183, 185). Total soluble solids, acidity and ascorbic acid were not significantly influenced by 2,4-D (184) or GA (183, 184). 

Growth retardants have been found to increase the drought resistance of a number of plants. The mechanism by which growth retardants accomplish this is not known. However, the effect of Cycocel and SADH in increasing the ability of a plant to withstand drought is thought to be related to the ability of these chemicals to delay the senescence of detached leaves. 

Feedback Relationship Between Ethylene and Other Plant Hormones If ethylene production in ripening fruit is an index of aging and senescence, then its suppression should result in retardation, or antagonism to ripening, aging, and senescence. 

Lers, A., Jiang, W.B., Lomanies, E. and Aharoni, N. (1998) Cibberellic acid and C02 additive effect in retarding postharvest senescence of parsley. Journal of Food Science 63, 66-68. 

G.A. McFarland and R. Holliday, Retardation of the senescence of cultured human diploid fibroblasts by carnosine. Exp. Celt Research, 212 (1994) 167-175. 

Austad, S. N. Retarded senescence in an insular population of Virginia opossums (Didelphis virginiana). Journal of Zoology 229 695-708 1993. 

At physiological pH in plants, polyamines exist as proton-ated forms. These protonated forms bind to the negatively charged phospholipid head groups and other anionic sites in membranes and alter the stability and permeability characteristics of such membranes. Polyamines also stabilize chloro-plast thylakoid membranes and retard chlorophyll loss in senescing barley leaf tissue. Polyamines also influence membrane fluidity, affect membrane localized proton pumps, and alter plant hormone responses, perhaps by competing for... 

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