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Seed germination in one wild and two cultivated varieties of celery (Apium graveolens L.) was found to be light-dependent and mediated through the phytochrome system. Seeds of cv. Florida at 20°C were very sensitive to light and germination could be promoted by green safe light as well as by short far-red irradiation of brief duration, while seeds of wild celery did not respond to far-red and were less responsive to green safe light. At the optimal temperature, continuous irradiation with white light caused maximal germination in all varieties. The need for light could be satisfied in cv. Florida by two daily short irradiations. In wild celery, more than six short irradiations were needed, while in cv. Alabaster short irradiations did not bring about the full light effect. Daily alternating temperatures also could replace the light requirement. Two varieties, cv. Florida and the wild, differ in their tolerance to high temperature. Seed germination of wild celery is more thermophilic than that of cv. Florida. Thermodormancy is induced by 35°C of shorter duration in seeds of cv. Florida than in those of wild celery. Light enhanced the induction of thermodormancy. Solute stress increased the number of short irradiations required for germination.

Seed germination of sweet pepper (Capsicum annuum L.) is inhibited after the seed is coated. The inhibitory effect of pellet-coating of ‘Early Calwonder’ pepper seed was caused by the physical properties of the coating materials. Clay coating limited part of the oxygen (O2) from reaching the germinating seed and provided a mechanical barrier to protrusion of the radicle. Clay-coated pepper seed germinated satisfactorily on filter paper in a high O2 environment or with minimum moisture on agar. Pellet coating formulations which would provide more O2 to the imbibing seed would assure comparable germination of raw and coated sweet pepper seed.

text abstractThe response of cotton (Gossypium hirsutum L.) to chilling temperatures has been documented mainly for germinating seeds and young seedlings (Christiansen, 1963; Christiansen & St John, 1981; Guinn, 1971; Sellschop & Salmon, 1928). Ratoon (known also as stub or biennial) cotton offers an opportunity to study the chilling injury of mature plants under field conditions. Observations showed that ratooning plants suffer stand loss during the winter. However, the surviving plants recover and start growing vigorously when temperatures rise, early in the following spring (Ellern, 1966; Evenson, 1970; McClintic, 1981).