The tetraploid plants in <i>Quamoclit</i> raised by the colchicine method

Abstract

The writer tried to raise the tetraploids of Quamoclit with large flower that are more valuable as the ornamental plant, by treating three species snd one variety, i. e., Q. pennata, Q. cocccinea, Q. coccinea var. hederifolia and Q. sloteri with colchicine. In the treatment, the following three methods were employed; 1) the immersion of seeds in the dilute aqueous solution of colchicine, 2) the dropping of the same solution on germinating plants, and 3) the mounting of lanolin emulsion of colchicine on germinating plants. In these three experiments, I failed in 1) but succeeded in the others, in raising the tetraploids (Table 1). For discriminating tetraploids from diploid the results of measurement of the length of guard cells were used (Table 2, 5 and 9).In tetraploids raised, thickening of cotyledons, leaves and stems etc., the retardation of growth, and the increase in the size of pollen grains and stomata were observed, as the same in many cases of induced tetraploids in other plants. The leaves, however, were generally smaller in size but wider in tetraploids than in diploids. The diameters of flowers in diploids to those of tetraploids were 2:3 in Q. pennata, 5:7 in Q. coccinea and Q. coccinea var. hederifolia.In tetraploids, abortive pollen grains were observed in fairly higher percentage than in diploids (Table 7).The tetraploids of Q. sloteri were completely sterile, but the tetraploids in all other species and variety were more or less fertile. In Q. pennata, 17 seeds were obtained from 19 tetraploid individuals, and 10 plants of the next generation of tetraploids yielded 46 seeds. In Q. coccinea and Q. coccinea var. hederifolia the tetraploids were more fertile. Q. coccinea gave 1000 or more seeds from per. plant of tetraploids and in Q. coccinea var. hederifolia, 200 or more seeds were raised from each individual.The seeds of tetraploids were much larger than those of diploids. The weight of 1000 seeds of tetraploids to that of diploids was 23:10 in Q. coccinea and Q. coccinea var. hederifolia showed about the same size in pollen grains, stomata and external characters compared with tetraploids.The observation of chromosomes was not made in tetraploids raised by the treatment, but the somatic chromosomes of the plants in the next generation of them were observed in root tip cells. The number of chromosomes were 60 in Q. pennata (diploid 30), 56 in Q. coccinea and Q. coccinea var. hederifolia (diploid 28).