Role of Age and Orientation of Cotyledons Explants on Multiple Shoot Production in Chickpea (Cicer arietinum L.)

Two-day-old seedling explants of chickpea (Cicer arietinum L. cv. BG-256) when placed with their micropylar end touching the medium (orientation c) in modified Murashige and Skoog's medium containing 5 �M of BAP showed maximum response in terms of number of shoots produced and their growth. But, when the pointed end of seedling explant kept downward into the medium (orientation b) response obtained was minimum. This orientation-mediated response was found to be dependent on the age of the explant because 2-day-old explants rarely and 3 or 4-day-old explants always produced multiple shoots (25-40 per explant) when placed in orientation b. This age-dependent effect of explant�s orientation was termed as �age-orientation effect�. This effect was demonstrated in two other chickpea cvs. (C-235 and BG-267) and therefore the response appeared to be cultivar independent. Further, both the growth rate of shoots and "age-orientation effect" were directly related to the proportion of number of the cotyledons remained attached with the seedling explants.