Three physical treatments viz. Sand paper scraping, beating and hot water treatments and two chemical treatments viz. Concentrated sulphuric acid and ethyl alcohol were included in the study. These treatments were applied on seeds of two sizes viz. large and small. Results of the experiments revealed that sand paper scraping and concentrated H2504 showed more effective performance than beating and hot water treatments in breaking seed dormancy of Sesbania rostrata. Ethyl alcohol had no effect on breaking seed dormancy. Large seed showed lesser dormancy than small one. Sand paper scraping 113 revolutions) of large seed gave the highest germination (97.8%).
PDF Abstract XML References Citation
How to cite this article
Sesbania rostrata is a high biomass producing crop and used as green manure, fuel, feed, fencing and trailing materials. It has extensively been used as a good source of organic matter in many countries to maintain soil fertility. It has nitrogen fixing stem as well as root nodules. The nitrogen fixation potential of Sesbania rostrata is higher than that of soybean and the contribution has been estimated 200 kg ha‾1 in 50 days (Rinaudo et al., 1982). Sesbania rostrata can supply the highest biomass along with the highest percentage of nitrogen than do S. aculeta and S. sesban (BRRI, 1987). But it is reported by workers in field and research stations that it exhibits poor germination (30-35%) while local species S. aculeta germinates upto 70-80% (Bhuiya and Bari, 1989). Depending upori maturity and storage condition, Sesbania rostrata may have upto 95% hard seeds (Amin, 1987). For this dormancy breakdown of S. rostrata is very much essential to get higher germination and uniform plant growth. Until now a very few investigation on hard seededness of S. rostrata seed has been conducted to develop an efficient technique to break dormancy. The present study was, therefore, under taken to find out the ways and means of breaking seed dormancy of S. rostratato improve the germination percentage.
MATERIALS AND METHODS
The seeds of S. rostrata were graded into two seed lots i.e., lot-1 and lot-2 depending upon seed size. Grading was done by 2 mm mesh sieve. In Lot-1, there were seeds above 2 mm diameter mesh i.e., large sized seeds. Seeds below 2 mm diameter mesh i.e., small sized seeds. Seeds below 2 mm diameter mesh i.e., small sized seeds were graded as lot-2. Seeds were air dried and were taken separately in polyethylene bags for studying. In case of sand paper scraping, the seeds were scarified by a manually operated sand paper scarifier for 0, 1, 5, 10, 12, 13, 15, 20 and 25 revolutions. Revolution for 12 and 13 times were included in the design latter to get the highest mode of germination due to sand paper scraping. Revolution means circular movement of the telescopic cylinder against the flat metal bars. During revolution, the flat metal bars were just dragged the sand against the abrasive wall of the telescopic cylinder and gouge the seed coat at numerous places. These goused areas served as the points of water entry, For beating, five hundred seeds were tied with cotton cloth and were beaten on a cemented floor for 5, 10, 15, 20, 25, 30, 35, 40 and 45 times maintaining a constant beating height of about 61 cm. Beating here means dashing the seeds themselves to the cemented floor for breaking the seed coat. Five hundred seeds, in case of boiling water treatment, were taken in a clean and thin cotton net and steeped in boiling water for 0, <1, 1, 2, 3, 6, 9, 12, 15 and 18 sec. For concentrated sulphuric acid (98%) treatments, the seeds were scarified by steeping for 0, 8, 12 m, 16 m 20, 24 and 28 minutes within it. The volume of seeds and acid was maintained at 1:2. During steeping, the seeds in acid were stirred with a glass rod constantly. When the treating was over, excess acid was decanted from each beaker. For ethyl alcohol treatment, five hundred seeds were steeped for 12, 24, 36, 48, 60, 72 and 84 hours in a glass bottle (air tight). After the treatment, the seeds were air dried and were set for germination in a sand germination media. The media was kept saturated upto 14 days after seed placement by adding water as and when necessary. The experiment was laid out in a completely randomized design using one hundred seeds per treatment with four replications. Data on germination were collected regularly upto 14 days. Normal seedlings were counted and the germination percentage was recorded. The statistical analysis of collected data were done and the mean values were adjusted by DMRT.
RESULTS AND DISCUSSION
Germination of S. rostrata seed significantly varied with seed size and sand paper scraping/beating, hot water treatment and chemical treatment. The interaction between seed size and sand paper scraping/beating also had significant effect on germination. But there was found no significant effect on interaction between seed size and hot water treatment or chemical treatment. Large seed had higher germination percentage than the small seed (Table 1). This result may be supported by Grant Lipp and Ballard (1964) who found that the larger seeds were less dormant than the small seeds irrespective of the cultivars of subterranean clover. Results in Table 2 showed that large seeds with 13 revolutions gave the highest percentage of germination (97.75%) which was statistically identical for small seeds with 20 revolutions resulting 94% germination. The result is supported by Amin (1987) who observed the sand paper scarification of S. rostrata resulted maximum 94% germination. The lowest percentage of germination was found in control treatment for both the large (13%) and small seeds (12.5%). Interactions between seeds size and sand paper scraping/beating treatments revealed that large seed with less number of revolutions resulted more percentage of germination than small seeds.
|Table 1:||Effect of seed size due to scarification on germination of S. rostrata seed|
|The figures having different letters differ significantly at 1% level by DMRT|
|Table 2:||Effect of seed size and sand paper scraping and beating on germination of S. rostrata seed|
|The figures having common letter(s) do not differ significantly at 1% level by DMRT|
|Table 3:||Effect of steeping period in hot water on germination of S. rostrata seed|
Germination percentage due to beating for both large and small seeds increased with the beating number in a minimum rate upto a certain level and then decreased (Table 2).
|Table 4:||Effect of chemical treatment on germination of S. rostrata seed|
The germination percentage increased when seeds were just steeped in boiling water and then gradually decreased with the increased period of steeping (Table 3). The result suggests that hot water treatment has a positive effect on breaking seed dormancy. This was supported by Gill et al. (1986) that boiling was an effective method for increasing Acacia farnesiana (L) seed germination. Steeping S. rostrata seeds in boiling water for less than 1 second showed the highest percentage of germination (62.63%) and the lowest percentage of germination (18.13%) germination by steeping seeds of S. rostrata in hat water. Treatment with boiling water for 75 sec increased germination from 4 to 78%. Treatment of seeds for more than 75 sec resulted deformed seedlings (Sheelavantar et al., 1989). Germination percentage increased gradually with the period of steeping in conc. H2504 upto 24 min and then decreased (Table 4). The highest percentage of germination (87.38%) was observed by steeping seed in conc. H2SO4 for 24 minutes which was at per with 28 min steeping resulting 86.13% germination. This result is in conformity with that of Amin (1987) who observed maximum germination (96%) of S. rostrata in sulphuric acid scarification. Treating S. rostrata seeds with conc. H2SO4 for 30 min increased germination from 12 to 94% (De and Rerkasem, 1992). Steeping in ethyl alcohol was identical to control and was the lowest. Ethyl alcohol had no effect on breaking dormancy of S. rostrata seed. This may be fact that erotion and incision to the seed coat by sulphuric acid treatment made the hard seeds permeable to water i.e., increased germination percentage.