Preharvest Factors Influencing Postharvest Quality of Tropical and Subtropical Fruit
Climate/environment Rootstock/scion Planting design Pruning practices Pest management Irrigation Plant growth regulators Plant nutrition The goal for postharvest physiologists, whether they are work in basic or applied research, is to maximize the postharvest quali horticultural commodities. Quality relates to several factors that ca commodity specific and mean different things to different people. T consumer may perceive quality as it relates to appearance, flavor dollar value. The packinghouse handler, wholesale distributor, retailer, in contrast, may perceive quality as ease of handling, un mity of packaging, and freedom from physical and physiologi defects as well as pathological breakdown. Although there is muc learn about the mechanisms of a given tropical or subtropical fru response to the postharvest environment, past research has pro handlers with the general principles of sound commodity mana ment. These principles include temperature, relative humidity, at sphere modification, cooling, and judicious use of fungicides a waxes following harvest. These management strategies are of cr importance for tropical products given their long transit conditions a the potential need for postharvest insect disinfestation quaran treatments. This paper will examine the role of the preharvest environment how it may affect the postharvest life of tropical and subtropical fr Essentially, preharvest factors can influence both the rate of development and maturation. The preharvest environment can have a physical impact on fruit quality: for example, wind or ins scarring may reduce the packout percentage. Finally and most im tant, but much more difficult to quantify, are those effects t influence susceptibility to physiological and pathological breakdow This review will not dwell on the latter, but recognizes that t influence of preharvest factors on postharvest decay incidence severity has been well documented. One must remember that the plant exists in a dynamic environm and therefore can respond to changes to that environment i interactive fashion. The factors listed in Table 1 are neither inclusive nor mutually exclusive. Several examples will illustrate interaction between one or more preharvest factors on postharves quality.
Growth regulator effects on retention of quality of stored citrus fruits
Abstract A 3-year study was initiated to determine the possible effects of two growth regulators, 2,4-dichlorophenoxy acetic acid (2,4-D) and gibberellic acid (GA3) on the quality of on-tree-stored and cold-stored fruits of cultivar ‘Clementine’ mandarin (Citrus reticulata Blanco) and cultivar ‘Washington’ navel orange (Citrus sinensis (L.) Osbeck). Treatments were applied at fruit color break as whole tree sprays, and fruits were either analyzed immediately after harvest or stored at 4°C and 85% relative humidity and analyzed at 4 and 8 weeks of storage. Regardless of the cultivar, GA3 alone or in combination with 2,4-D significantly slowed the rate of rind color change and the rate of rind softening, both on the tree and post-harvest. However, the rate of change in color and firmness of the rind on the tree and post-harvest was variety dependent. When used alone, 2,4-D had no effect on these factors. No growth regulator effects were noted on weight loss, extractable juice, juice titratable acidity (TA) and total soluble solids (TSS), or the ratio TSS/TA. It is concluded that the delayed senescence obtained from GA3 is primarily at the rind level.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.