Effect of gibberellin on germination of some light sensitive seeds when applied by foliar spray or capsule soaking

Abstract

Light sensitive seeds fail to germinate in the dark or in seed beds when they are covered with soil. It was reported by some investigators that gibberellin is effective to make them germinable in the dark. The treatment with GA solution of some seeds of very small size is, however, not so practical, because they are difficult to handle when they are wet. In this study, attempts were made to apply GA through the leaves or capsule to the seeds. Materials used were Primula malacoides, Sinningia speeiosa (gloxinia), Calceolaria herbeohybrida, and Nicotiana tabacum (tobacco). In a series of experiments, GA solution was sprayed on the stock plants at the flowering stage or at the immature capsule stage. In another series of experiments, capsules were soaked in GA solutions of various concentrations immediately after picking. The seeds were then taken from the treated plants or capsules and were stored for a few months. These seeds were germinated in the light and in the dark, and also in the seed bed.
In Primula, seeds taken from the plants sprayed with GA solution at the flowering or immature capsule stage showed about 40% germination in the dark (Table 3). The seeds taken from the capsules soaked in GA solution of 500ppm after picking showed high percentages of germination in the dark. The treatment at the immature stage was slightly more effective than that at the mature stage (65_??_76%) (Table 4).
The seeds taken from the treated plants and capsules showed high percentage of germination in the seed bed as well as in the germinator (Table 6). The effect of GA treatment on the germinability of seeds in the dark was maintained for at least 15 months of storage (Table 7).
In gloxinia, foliar application of GA at the flowering stage had little effect, while soaking the capsule in GA solution was effective, resulting in more than 30% of germination of seeds during 15 days in the dark (Table 9). Germination at the rate of 37% was obtained with the seeds taken from the capsule cut with a peduncle of 5cm long whose cut end was soaked in GA solution for 24 hours (Table 10).
In calceolaria, soaking of the capsule immediately after picking was found to be effective to improve germination of seeds in the light as well as in the dark after 6 months of storage (Table 12).
In tobacco, foliar application showed little effect on the germination of seeds in the dark, white soaking treatment of the capsule immediately after picking was highly effective. The effect was greater on the immature seeds than on the mature ones, and the higher the concentration of GA the greater the effect (Tables 14, 15 and 16).
These results seem to show that GA applied to leaves and capsules are translocated to the seeds. through living tissues, though it was not clear whether GA was translocated per se or after transformed.