Studies on morphogenesis in a blue-green alga. I. Effect of inorganic niteogen sources on developmental morphology of Anabaena doliolum.

Abstract

Spore germination, heterocyst production, hormogone formation, and sporulation are the morphogenetic stages in the developmental cycle of Anabaena doliolum Bharadwaja. In basal medium sporulation is simultaneous while heterocyst formation is sequential. Nitrate, nitrite, and ammonium nitrogen inhibit sporulation and heterocyst formation. The degree of inhibition depends on the concentration and source of inorganic nitrogen. Nitrate and nitrite induce lysis which is concentration dependent and circumscribed by time, i.e., up to a certain stage the lytic events are preventable by transfer to basal medium, but beyond this stage they become inevitable and complete lysis occurs even in the absence of nitrate or nitrite. The sequential differentiation and spatial relations of heterocysts in a growing filament are characteristic of each nitrogen source and indicative of the polarity involved in the gradient of heterocyst formation.