Closing remarks

Abstract

I believe this is the first major meeting on plant water relations to be held in Britain since 1964 when the Society of Experimental Biology organized a symposium on ‘ The state and movement of water in living organisms’. Shortly before that, in 1961, the British Ecological Society chose ‘The water relations of plants’ as the theme of its annual symposium. When the papers read to us in the last two days are published, we will be able to compare them with their predecessors from a decade ago. In some branches of the subject we will be able to discern impressive progress. In others, we may agree with Tennyson that ‘Science moves but slowly, slowly, creeping on from point to point’. One topic dealt with at some length in the two previous meetings has not been discussed here: the flux of water vapour in the air surrounding leaves and above plant canopies. Although some interesting problems of micrometeorology remain unresolved, the main problem of relating evaporation rate to climate was solved, in essence, by Howard Penman nearly 30 years ago when he used some elegant algebra to combine the conservation of energy and of mass at a water surface. Armed with the Penman formula and its descendants, the meterologist can now say to his ecological colleague: ‘tell me the essential parameters of your system and I will calculate the loss of water from your vegetation in any type of weather’