Influence of pre-harvest nitrogen supply on post-harvest behaviour of ornamentals: importance of carbohydrate status, photosynthesis and plant hormones.
Druge, U.;
Gartenbauwissenschaft Year: 2000 Vol: 65 Issue: 2 Pages: 53-64 Ref: 75 ref.
2000
บทคัดย่อ
The potential role of carbohydrates, photosynthesis, ethylene, abscisic acid and cytokinins in N-affected postharvest behaviour of ornamentals is discussed, differentiating between preharvest influences of N amount, N form and a secondary salt stress. The increasingly proposed function of the root as a sensor continuously monitoring root zone stress conditions is emphasized. Recently found interactions between sugars, cytokinins and light and between ammonium and ethylene in leaf senescence are considered as well as signal effects of nitrate on carbon allocation. Excessive N supply during cultivation, which also causes secondary salt stress, leads to an unfavourable physiological condition for postharvest behaviour. Decreased carbohydrate reserves coinciding with a low photosynthetic capacity may cause post-production carbohydrate deficiency. Increased fluxes of abscisic acid via the xylem and higher concentrations in plant tissues coinciding with opposite reactions of cytokinins and high ethyle
ne production increase the risk of growth inhibition and postharvest senescence. Whereas a balanced ammonium:nitrate ratio potentially favours postharvest behaviour via higher cytokinin delivery by the root system, pure ammonium fertilization can cause ammonium toxicity, carbohydrate deprivation and high ethylene production. The relevance of these internal changes to postharvest life is estimated distinguishing between different ornamental products. Changed hormonal situation and carbohydrate deficiency are probably important factors impairing postharvest life of potted plants after excessive N supply. An apparently lower sensitivity of cut flowers can be explained by the disconnection from the stressed root system. The variable response of leafy cuttings to high N supply is additionally proposed to be attributed to the different swiftness of rooting resulting in hormonal changes and to different contribution of photosynthesis to carbohydrate pools in dependence from plant species and light conditions.