ISHS Acta Horticulturae 226: International Symposium on Propagation of Ornamental Plants
PRESOWING TREATMENTS TO IMPROVE CASSIA AND CALLIANDRA SEED GERMINATION |
| Author: | T. Venkatesh Reddy |
| Abstract:
Cassia renigara and Calliandra surinamensis are ornamental plants of great beauty. While the seeds of Cassia have thick seed coat, the calliandra seeds have physiological dormancy. Untreated seeds when sown seldom germinate and the germination period extends over a long period. Experiments were, therefore, conducted to find out if the germination percent could be increased and the period of germination decreased by various presowing seed treatments. Good seeds collected from a single tree of each species were treated as indicated in the tables 1 and 2. For acid scarification con. H2SO4 was used. Soaking time either in water or in chemical solutions was 24 hours. Prechilling treatment was imposed by placing the seeds in a beaker with water and placing the beaker in a refrigerator (5°C) for the specified period. All the treatments were replicated thrice. Fifty seeds were used for each treatment. The treated seeds were sown in raised beds. The experiment was conducted during February-March during which time the mean day temperature was around 30°C and mean night temperature was around 18°C. Observations on the number of seeds germinated were recorded daily. Using these observations Bartlett's earliness index was computed (Bartlett, 1937). After taking the final observation on germination the root number and the maximum root length of each seedling were recorded. In case of Cassia renigera seeds, acid scarification for 30 min + water soaking for 24 hr resulted in the highest (72%) as well as the earliest (as indicated by Bartlett's earliness index) seed germination (table 1). Increased germination has been reported in Cassia fistula (Nalwadi et al. 1975) and Cassia marginata (Nalini and Vimala, 1968) due to acid scarification and mechanical scarification of the chalazal end, respectively. Sodium cyanide (NaCN) alone at higher concentrations and prechilling for 3 hr inhibited the seed germination. However, soaking the acid scarified seed in NaCN improved seed germination. Sodium cyanide has, however, significantly increased the seed germination percent as well as the rate in Chrysalidocarpus lutescens (Venkatarayappa et al., 1982). Acid scarification and NaCN (50 ppm) hastened, while soaking in water delayed the seed germination. Acid scarification tended to increase while NaCN reduced the root number per seedling. All the treatments reduced the maximum root length of the seedling (table 1). Exposing the seeds of Calliandra surinamensis to low temperature of 5°C (prechilling) for 3 hr gave the maximum and fastest seed germination followed by prechilling for 8 hr and GA (table 2). Sodium cyanide although did not affect the seed germination | |
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