Search

The protective effect of a synthetic terpenoid analog of abscisic acid (ABA), coded LAB 173711, on transplant shock in rice was investigated under field conditions. Rice seedlings (Fujisaka 5 and IR 20) were taken from a seed bed and their roots were immersed in aqueous solutions of the growth regulators for 24 h. Afterwards they were drought-stressed for 3 or 6 h by exposing them to direct sunlight before they were transplanted to the field. A pretreatment with either LAB 173711 alone or in combination with the growth retardant tetcyclacis reduced the loss of water during the exposure to sunlight, increased the percentage of survival of the seedlings in the field, and increased the percentage of grain filling of the plants which had survived. The combined application of growth regulators was most effective and may be useful for minimizing transplant shock in rice and other crops.

GLK-8903, an experimental product whose main ingredient is produced by hydrogenation of a primary alcohol extracted from plants, showed significant potential in protecting bean (Phaseolus vulgaris L.) plants from chilling injury. The GLK-8903 protection mechanism was assessed by examining several physiological and biochemical responses. The decline in leaf water potential and the increase in osmotic potential caused by chilling exposure to 4C (day/night) were minimized by the application of GLK-8903. Chilling causes an increase in electrolyte leakage, an indication of chilling injury of the plasma membrane. Increased electrolyte leakage was reduced significantly in the GLK-8903-treated plants during chilling. This minimized leakage may be due to less damage of the plasma membrane. Plasmolysis and deplasmolysis studies of the epidermal cells suggest that GLK-8903 is able to reduce the plasma membrane perturbation in the chilling environment, as evident by: 1) the lower permeability coefficient to urea at 4C, and 2) the swelling of protoplasts in the cells of untreated tissues after chilling exposure with no swelling of the protoplast being observed in the GLK-8903-treated cells. Malondialdehyde (MDA), a product of lipid peroxidation, increased more in untreated controls than in treated plants exposed to 4C. Plasma membrane ATPase activity decreased less in GLK-8903-treated plants than in untreated controls after 3 days at 4C. The mechanism of GLK-8903-alleviated chilling injury is discussed.

The protective effect of a synthetic terpenoid Analog of the plant hormone abscisic acid (ABA) coded LAB 173711 applied alone or in combination with the growth retardant tetcyclacis on chilling injury of rice was studied under growth chamber, greenhouse, and field conditions. The compounds were applied as a foliar spray before and after the onset of chilling treatment, as a substrate via the root system, and as a medium for seed soaking. The ABA analog increased chilling resistance in a manner similar to ABA. Combination of the analog with tetcyclacis revealed additive effects. Increased chilling resistance involved several processes: stomatal closure which reduced water loss during chilling, stabilization of the membranes, stabilization of the chlorophyll level, and stabilization of the root system. Possibilities for practical use of the compounds in rice production are discussed.

Chilling, in plant stress, usually refers to an environment with temperatures low enough to cause plant tissue damage, but not low enough to cause freezing of tissue water. Many economic crops such as rice, maize, and vegetables are sensitive to chilling. Their growth and development can be drastically hindered by chilling. Consequently, quantity, as well as quality, of the yield are reduced if it is not a total crop failure. The impact of chilling injury on crop production is just as great as freezing. Numerous efforts have been made to overcome the chilling problem in agriculture, for example, breeding for early vigor in maize, modifying cultural practices to enable survival of tornato seedlings after early transplanting in the field, or application of chemicals to alleviate chilling injury in rice. In 1989, the Laboratory ofPlant Hardiness at the University of Minnesota initiated an effort to examine the potenti al of GLK-8903, a chemical having no growth-regulating property, in protecting vegetable plants from chilling injury.

Protection mechanism of a new compound, coded as GLK-8903, from chilling injury in bean plants was assessed by measuring several physiological parameters. The decline in leaf water potential caused by the chilling exposure to 4°C (day/night) was minimized when GLK-8903 was applied to the plants as compared to the non-treated control. Chilling causes an increase in electrolyte leakage, an indication of chilling injury that occurs at the site of plasma membrane. An increased electrolyte leakage was reduced in the GLK-8903-treated plants during chilling. Data from plasmolysis and deplasmolysis studies of epidermal cells suggest that GLK-8903 is able to stabilize the plasma membrane under stress condition by determining the permeability coefficients plasmometrically (1.96 cm s-1 × 10-4 for GLK-8903-treated plants vs. 4.00 for the controls 3 d at 4°C) with less decreased activity of the plasma membrane ATPase (9.36 μmol ATP.mg chl-1·h-1 for GLK-8903-treated plants vs. 5.04 for the controls 3 d at 4°C). GLK-8903 appears to have high application potential in protecting bean plants from chilling injury with improved yield.