Antitranspirant N-2001 (10%), Great Lakes Chemical Corporation, was applied as a soil drench to `Fuji'/EMLA7' apple plants growing in 15 cm pots in a 25/22±3°C (D/N) greenhouse. After bringing pots to field capacity, chemical application was made and water was withheld thereafter. One hour after chemical application, stomatal conductance of treated and control plants was 0.25 and 0.70 cm/sec, respectively. Stomatal conductance of treated plants was maintained at approximately 0.25 cm/sec throughout the test period (28 days). Stomatal conductance of the control plants decreased to 0.25 cm/sec 13 days after treatment due to desiccation. The stem xylem water potential of the treated and control plants was -2.0 and -5.5 MPa, respectively, 28 days after treatment. The relative water content of leaves of treated plants was 45% greater than controls. The average loss of water via transpiration of treated plants was 32% less than the control plants.
Sung H. Guak, Charles C. Shin, and L. H. Fuchigami
Cheng-lie Zhang, Paul H. Li, and Charles C. Shin
Twenty-day-old `Bush Blue Lake 47' common bean plants grown in a growth chamber at 25 days/22C night and a 12-hour photoperiod regime were foliar sprayed with 0.5% GLK-8903 including 0.05% Tween-20. After 24 hours of treatment, plants were chilled in a cold room (4C day/night, 12 hours of light). After 3 days of chilling, leaves of untreated controls were injured, as visually characterized by leaf wilting, whereas leaves of the GLK-8903-treated plants still retained turgor. During chilling, the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) decreased. GLK-8903 treatment had no effect on SOD and POD activities; however, the CAT activity was reduced significantly after GLK-8903 treatment either at 25 or at 4C. During chilling, the content of malondialdehyde, a decomposition product of phospholipid peroxidation, increased in treated plants and untreated controls, with increased content significantly lower in the former compared with the latter. The GLK-8903 per se and total lipid extracted from GLK-8903-treated plants were able to reduce the linoleic acid oxidation in vitro. The mechanism by which GLK-8903 alleviates chilling injury in bean plants is discussed.
Agnes A. Flores-Nimedez, Paul H. Li, and Charles C. Shin
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.
Agnes A. Flores-Nimedez, Paul H. Li, and Charles C. Shin
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.
Sanliang Gu, Leslie H. Fuchigami, Lailiang Cheng, Sung H. Guak, and Charles C.H. Shin
Seedling plugs of `Early Girl' tomato plants (Lycopersicon esculentum Mill.) were potted in peatmoss and perlite (60:40% by volume) medium, fertilized with 8, 16, 24, or 32 g NutriCote Total controlled-release fertilizer (type 100, 13N–5.67P–10.79K plus micronutrients) per pot (2.81 l), and treated with 0%, 2.5%, 5%, or 7.5% antitranspirant GLK-8924 solution, at the four true-leaf stage. Plants were tipped at the second inflorescence and laterals were removed upon emergence. Leaf stomatal conductance, transpiration rate, and growth were depressed by GLK-8924. In contrast, higher fertilization rate increased plant growth but leaf stomatal conductance and transpiration rate were not affected until 3 weeks after GLK-8924 treatment. With 24 g NutriCote per pot, lamina N concentration in GLK-8924 treated plants was 12.5-fold of that in untreated plants, regardless of GLK-8924 concentration. Lamina P, K, Fe, and Cu were greater while S, Ca, Mg, Mn, B, and Zn were not affected by GLK-8924. The reduced growth by GLK-8924 may be due to the reduced stomatal conductance while the increased growth by high fertilization may be due to influences on plant nutritional status.