Considering the environmental and specific socioeconomic significance of the critically endangered mangrove Lumnitzera littorea, this study was conducted aiming the conservation of the species. The specific objectives were to define the diversity of the other mangrove species in association with the existing L. littorea plant population in the Madu Ganga wetland, Sri Lanka, to study its seed germination and identify the barriers for seed germination. The existing population of L. littorea is an aged population with low regeneration potential. Most of the seeds collected at the dispersal maturity were empty. A micro moth belonging to Family Gelechiidae was identified as the embryo predator. Although GA3 (Gibberellic acid) treatment and dry storage reduced the germination time, none of the seed treatments significantly improved the seed germination of L. littorea. Low seed germination observed was due to absence of embryo in mature seeds as a result of insect predation and physiological dormancy of seeds. Optimum GA3 concentration, duration of dry storage and potting medium with suitable salt concentration for seedlings should be optimized in future research.
The abiotic stresses course major environmental factors that determine the most serious yield reduction in rice (Oryza sativa L.). The abiotic stresses tolerant ability can be improved by changing typical chromosome number of plants. The objectives of the studies were to evaluate the performance of callus of rice cultivars (Suwadel and Sulaai) for different Colchicine concentrations to produce polyploidy for enhance tolerant characteristics to drought and salinity stresses. Surface sterilized seeds were introduced to Murashige and Skoog (MS) basal medium with hormone 2mgL-1 2,4-D (2, 4-dichlorophenoxyacetic acid) and 0.1 mgL-1 BAP (6-benzylamino purine) for callus induction. Callus of 0.5cm 2 from rice cultivars introduced to different Colchicine concentrations (0, 30, 60, 90 and 120 mgL-1) and different time durations (12, 24 and 78 hours). Treated callus were introduced to shoot regeneration on MS medium with 0.1mgL-1 IAA (Indole acetic acid) and 2mgL-1 BAP. Colour, texture and regeneration ability of callus were recorded after one month. Completely Randomized Design (CRD) with five replicates was used for study. Statistical analysis was performed with Duncan's multiple range tests using SAS software (version 9.1.3). Results showed that callus treated from Colchicine 30, 60, 90 and 120 mgL-1 in 12 hours and, 30, 60, 90 mgL-1 in 24 hours have potential to survive. Increasing Colchicine concentration and time duration showed that regeneration ability of callus reduced in selected rice varieties.
A study was conducted to observe the effect of different concentrations of indole-3-butyric acid (IBA) and maturity levels of single node stem cuttings for vegetative propagation of E. ritigalensis. Branches of the plant were treated by 20% Clorox in 20 minutes and rinsed it two times using distilled water. Stems cuttings were grouped into three according to the diameter (20-30 mm, soft wood; 30-40 mm, semi hardwood and 40-50 mm, hardwood).Three different ways of leaves remaining in single node stem cuttings were used; half of single leaf, half double opposite leaves and without leaf. Stem cuttings were treated by IBA (0, 2, 2.5, 5, 10 and 15 mgL-1) for 15 minutes. Plant propagators were prepared by poly bags (150 gauges) and filled by sterilized coir dust. Thereafter, they were kept in two months and observed the survival rates of cuttings (greenish or not),number of roots, length of the lengthiest root, number of buds and number of leaves per bud. Experiments were arranged in three factor factorial completely randomized design (FCRD) with ten replicates. Statistical analysis was performed with Duncan's multiple range test using SAS software (version 9.1.3). It was observed that rooting was at initial stage of all cuttings after one month. Result were showed that the semi hardwood single node stem with half single leaf or double leaves treated by 10 mgL-1 and 15 mgL-1 IBA were best for rooting compare to other all treatments and control, showed 100% survival rate with three buds per cutting.
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