A Thermodynamic Insight into the Relationship: Dark Transpiration, Respiration, and Growth in Plants

Abstract

The importance of respiration in biomass accumulation and productivity has increasingly been clarified in respiration-based growth models, but the precise nature of this relationship is not clear. Existing models may closely simulate aspects of plant growth and are therefore useful, but they are limited in their ability ‘to test hypotheses about respiration and its link to growth and productivity’ (Amthor, 1989). They cannot provide further insight until they can be placed into the context of an accurate and complete description of the character and mechanism of this relationship. The relation between the main physiological processes during the dark: transpiration and respiration is scare studied, but it is of a special interest. The existence of such a relation is experimentally established by studies in laboratory- (Prokof ev and Katz, 1963; Jeanrenaud, 1978) and nature- (Polster, 1959) environment. As far as the energetics of the relationship between respiration and transpiration is concerned it is a most complicated problem. The commonly accepted vision is that the respiration is the source of energy for transpiration (Jeanrenaud, 1978). The contrary thesis although in an implicit form is covered in studies of Polster (1959) and Zholkevitch (1968). The first data that document a higher respiration rate, respectively a higher energy of respiration at a higher dark transpiration rate are reported by Stoyanov and Florov (1969). Later, in the Surface-boundary approach in biothermodynamics (Florov 1978; 1988) it is motivated the concept that the free energy of dark transpiration provides with energy the dark respiration. This report is aimed to summarise some of our experimental results concerning the responses of dark transpiration, respiration, growth and productivity of plants as provoked by air relative humidity (RH) during the dark period. This kind of study is also aimed to be an energetic insight into the mechanism of respiration-growth interdependence.