ISHS Acta Horticulturae 543: VII International Symposium on Postharvest Physiology of Ornamental Plants
POSTHARVEST RESPONSES OF DIFFERENT ORNAMENTAL PRODUCTS TO PREHARVEST NITROGEN SUPPLY: ROLE OF CARBOHYDRATES, PHOTOSYNTHESIS AND PLANT HORMONES. |
| Author: | U. Druege |
| Keywords: | potted plants, cut flowers, cuttings, ethylene, cytokinin, abscisic acid, stress |
| Abstract:
This short review focuses on the potential role of carbohydrates, photosynthesis and the plant hormones ethylene, abscisic acid (ABA) and cytokinins in nitrogen-affected postharvest behaviour of potted plants, cut flowers and cuttings. Preharvest influences of nitrogen amount, of nitrogen form and of a secondary salt stress are discussed with emphasis on the increasingly proposed function of the root as a sensor continuously monitoring root zone stress conditions. Excessive nitrogen supply during cultivation, which also causes secondary salt stress, leads to a physiological condition of plants, which is potentially unfavourable for subsequent postharvest life. Decreased carbohydrate levels coiniciding with a low photosynthetic capacity may cause postproduction carbohydrate deficiency. Increased fluxes of ABA via the xylem and higher concentrations in plant tissues coinciding with opposite reactions of cytokinins and high ethylene production may increase the risk of growth inhibition and postharvest senescence. Whereas a balanced ammonium:nitrate ratio potentially favours post-harvest life via a higher cytokinin delivery by the root system, pure ammonium fertilization can cause carbohydrate deprivation, higher ABA levels and increased ethylene production. In addition to influences of nitrogen level, genetically determined sensitivity and postharvest environmental conditions, the postharvest exposure of the ornamental product to the hormonal signals and carbohydrate demand of the stressed root system is proposed to be a crucial factor. This might at least in part explain the apparently higher nitrogen sensitivity of potted plants as compared to cut flowers and cuttings. | |
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