Dillenia indica Linn. is a nearly evergreen tree widely distributed in South-east Asia. Regeneration is by seeds borne within large indehiscent fruits. When extracted fresh, seeds are glued together by the sticky mucilage on the seedcoat. Mucilage anchors seeds during rains, thus preventing them from escaping the fruit. Mucilage does not promote or inhibit germination, but it does restrict the inflow of water into seeds during the initial stages of imbibition. In nature, seeds germinate (within fruits) in July–August following heavy rains that wash off most of the mucilage. Light had a significant effect on germination: a 12/12 h light/dark regime resulted in more and faster germination than when seeds were incubated in total darkness. Seeds exhibited one flush of germination within fruits and another flush in the laboratory following extraction, drying and rehydration, suggesting the occurrence of two physiological types of seeds with regard to light requirement for germination. The embryo of D. indica is underdeveloped, and seeds take ~30 days to germinate under appropriate conditions. Thus, the seeds have morphological dormancy (MD). The possible roles of seed-coat mucilage and light in the germination biology of D. indica seeds in nature are discussed.

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In contrast to reports in the literature that seeds of Dodonaea viscosa from China and Pakistan are non-dormant, or nearly so, we found that a high percentage of seeds of this species collected in north-western India have a water-impermeable seed coat at maturity, i.e. physical dormancy. Thus, seeds that were mechanically scarified and boiled (to open a ‘water gap’ in the seed coat) germinated to much higher percentages (84% and 77%, respectively) than did those that were non-scarified (24%). Our results agree with studies of seed dormancy in this species in various other parts of its large geographical range.

The wide range of climatic condition in the natural distribution of chir pine is expected to result in high genetic variation within different populations of the species. The present study on the provenance variation of chir pine aims to determine the nature and extent of variation in wide range of populations with respect to 23 morphological traits of cone, seed and seedling, (at nursery stage) of 63 provenances of Pinus roxburghii. Seed sources exhibited a wide range of variability in terms of mean vales for various traits, standard deviation, variance, coefficient of variability, broad sense heritability, genetic advance and genetic gain and offer ample scope for undertaking screening for the desired traits. Genotypic variance (Vg) and genotypic coefficient of variability (GCV) for most of the parameters were found to be higher than corresponding environmental variance (Ve) and environmental coefficient of variability (ECV), except cone fresh weight, survival%, days taken for bud break and collar diameter where Ve and ECV dominated the Vg and GCV, thus indicating influence of environment on the expression of these traits. Moderate to high percentage of heritability coupled with same intensity of gain, was observed for many of the traits studied under laboratory conditions and at nursery stage e.g. for germination percentage, MGT, GV. This signifies that these traits are under strong genetic control and good amount of heritable additive genetic component can be exploited for further selection and improvement of this species.

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