Morphological and physiological characterization of seed heteromorphism in Medicago denticulata Willd
2020
Sethi, Renu | Kaur, Navjyot | Singh, Manpreet
Under natural conditions, Medicago denticulata produces heteromorphic seeds differing in seed coat colour—cream and brownish black. The present study was conducted in order to determine morphological and physiological differences among heteromorphic seeds of M. denticulata in relation to dormancy and germination behaviour. Brownish black seeds with high moisture content were non-dormant and germinated to a high percentage. However, cream seeds with low moisture content were dormant and exhibited lesser germination without dormancy breaking treatments. Scanning electron microscope studies revealed papillose surface pattern in both seeds. However, brownish black seeds differed from cream seeds by having small cracks scattered all over the surface. Various dormancy breaking treatments viz., sandpaper scarification, soaking in sulphuric acid and hot water significantly increased the germination of cream seeds indicating seed coat imposed dormancy in these seeds. Accelerated ageing of brownish black seeds for 20 or more days resulted in complete inhibition of germination. Whereas, some cream seeds (~ 13%) aged for 20 days were still able to germinate. With accelerated ageing, both seeds recorded decrease in starch and total soluble proteins with concomitant increase in membrane leakage, total soluble sugars and free amino acids. Persistence studies under field conditions revealed that cream seeds present on soil surface or at a burial depth of 2 and 10 cm were able to germinate up to 12 months; but no germination was observed in brownish black seeds buried for 12 or more months. Results of accelerated ageing studies and field persistence suggest longer persistence for cream seeds as compared to brownish black seeds.
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