Germination ecology of Medicago denticulata Willd. in relation to seed coat colour, persistence and herbicide exposure
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
The present study entitled, “Germination ecology of Medicago denticulata Willd. in relation
to seed coat colour, persistence and herbicide exposure" was conducted at Punjab Agricultural
University, Ludhiana and Dr. J.C. Bakhshi Regional Research Station, Abohar. Under natural
conditions, M. denticulata produces heteromorphic seeds differing in seed coat colour - cream
and brownish black. The study was aimed to compare the effect of seed coat colour on
dormancy and germination behaviour of M. denticulata seeds and response of heteromorphic
seeds to various environmental variables and herbicide exposure. Brownish black seeds were
non-dormant with high moisture content. Cream seeds with low moisture content were
dormant and germinated only when subjected to dormancy breaking treatments indicating
seed coat imposed dormancy. Germination of both cream and brownish black seeds was
independent of light. Cream seeds germinated in the wide temperature range of 15/5 to
30/20°C; while brownish black seeds germinated in narrow temperature range of 15/5 to
25/15°C. Brownish black seeds recorded no germination at 200 mM NaCl; whereas, some
cream seeds (10%) were able to germinate at this NaCl concentration. The osmotic potential
required for 50% inhibition of maximum germination of cream and brownish black seeds was
-0.37 and -0.32 MPa, respectively. Brownish black seeds accelerated aged for 20 recorded
no germination. Whereas, some cream seeds (∼13%) aged for 20 days were still able to
germinate. Cream seeds placed on soil surface or buried at 2 and 10 cm depth germinated up
to 12 months; but no germination was observed in brownish black seeds buried for 12 or more
months. Therefore, cream seeds may have longer persistence than brownish black
seeds. Herbicide sprays at eight and twelve-leaf stages of M. denticulata reduced seed
production potential of this weed with concomitant decrease in germination as compared to
herbicide sprays done at four-leaf stage of M. denticulata. This indicated possibility of
herbicide carry-over effect from parent plants.
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