Alleviation of Salinity and High Temperature Stress by Plant Growth Regulators Permeated into Lettuce Seeds via Acetone1

Abstract

Permeation via acetone of fusicoccin (FC), or of a combination of the three growth regulators, kinetin (K), 2-chloroethyl(phosphonic acid) (ethephon) (E), and gibberellic acid (G) into dry lettuce (Lactuca sativa L. cvs. Grand Rapids and Mesa 659) seeds markedly relieved the inhibiting effects of stress on germination and seedling emergence. Permeation with FC or K+E+G increased dark germination by 80 to 90% at 30°C. At 35°, germination of ‘Grand Rapids’ seeds was enhanced much more by FC than by K+E+G. Both FC and K+E+G increased germination in solutions of NaCl (−4.95 bars) or polyethylene glycol-6000 (−3 bars). In saline medium at 30 and 35°, FC was more active than K+E+G. Hypocotyl and radicle elongation was greater for seeds treated with FC than for seeds treated with other materials in both aqueous and saline media. In soil moistened with water or 0.1 NaCl, emergence of unpermeated ‘Mesa 659’ seeds was 0 to 2% at 25°. Permeation with FC or K+E+G enhanced emergence 65–80% in water, 48–55% in NaCl. FC produced more vigorous seedlings in terms of fresh weight and size than any other treatment including K+E+G. Furthermore, FC generally shortened the emergence time more than K+E+G treatment, the difference being more marked in saline soil.

Alleviation of High Temperature Stress by Preplant Permeation of Phthalimide and Other Growth Regulators into Lettuce Seeds via Acetone

“…Its interaction additively or synergistically with KIN and/or ethephon to improve germination and emergence and to alleviate the adverse effect of high temperature was remarkably similar to that of GA. This similarity is consistent with previous results that more than one growth regulator, each fulfilling a specific requirement, is needed under stressful conditions to maximize germination and seedling emergence (4,6). 'Mesa 659' seeds, which show little or no sensitivity to GA, KIN or ethephon at moderate temperatures of 20° or 25°C, become sensitive to these regulators at 30° or 35°C.…”

“…'Mesa 659' seeds, which show little or no sensitivity to GA, KIN or ethephon at moderate temperatures of 20° or 25°C, become sensitive to these regulators at 30° or 35°C. 'Grand Rapids' seeds are sensitive to GA at moderate temperatures and became responsive to KIN and ethephon as the temperature is increased to 30° or 35° (4,6). In 'Mesa 659', ethephon 4-KIN was as active as phthalimide + KIN, GA + KIN, phthalimide + ethephon 4-KIN or GA + ethephon -f KIN (Fig.…”

“…Currently, plants initiate inflorescences under the cool, short day conditions of fall and then bloom in spring. The flowering pattern of azalea is similar to that of hydrangea, but a large portion of azalea production is scheduled for year-round flowering by highly controlled temperature, photoperiod, and chemical growth retardant treatments (2,4). Research has shown hydrangea floral initiation to be stimulated by short photoperiods at temperatures above 21°C (8,14).…”

Need for High-quality Seed for Effective Priming to Overcome Thermodormancy in Lettuce

“…Khan Beans respond best to moderate temperatures, and 23°C is considered to be the ideal growing temperature. The effects of low temperature on germination, growth, and yield have been reported (2), but few reports have covered the effect of lower temperatures on pod and seed set. Hume et al (6) observed in soybeans that some cultivars did not set at temperatures of 157 15°C D/N, while the most cold-tolerant set seed at 1579°.…”

Emergence at High Temperature and Seedling Growth Following Pretreatment of Lettuce Seeds with Fusicoccin and Other Growth Regulators

“…Permeation of growth regulators into lettuce seeds via acetone has been shown to be an effective method of overcoming the effects of high temperature stress on germination and emergence. Fusicoccin, a diterpine glucoside, has been especially effective in promoting germination and emergence at supraoptimal temperatures (1). This compound promotes the germination of seeds of both light-sensitive and nonlight-sensitive cultivars (1).…”