SENSING PH

Abstract. pH is an all‐pervasive variable in the environment of phototrophs. Phototrophs as a whole, and even the single genus Dunaliella, can grow over essentially the whole range of pH values found in nature. Such a large range of pH values, combined with other chemical variations in the environment, impose a range of constraints on plant behaviour related to intracellular pH regulation, nutrient acquisition, and avoidance of toxic effects. No single genotype can grow well over the whole pH range compatible with growth of phototrophs as a whole, although some deliberately alter surface pH so as to create a 5–6 unit pH gradient over the surface related to nutrient acquisition and avoidance of toxic influences. The regulation of these various processes does not, on current evidence, involve pH‐sensing by any extracellular sensor which is not part of the catalytic or regulatory mechanism of a membrane protein such as a porter. Copyright © 1990, Wiley Blackwell. All rights reserved