21 8 SECTIONAL ADDRESSES 



plant.' That is, the function of respiration is to provide the energy for 

 plant movements and for the building up of materials of higher energy 

 content than the assimilates synthesised in photosynthesis. Pfeffer's 

 statement is less precise. ' A continual supply of energy is necessary for 

 the maintenance of vital activity, and hence the possibility of aerobic or 

 anaerobic respiration is a primary essential for all vital processes, including 

 those which do not involve any direct consumption of kinetic energy.' 

 This is simply a statement that for a plant to remain alive a continuous 

 supply of energy is necessary, and that this is provided in respiration. 

 Palladin's viev7 vfus much the same as Sachs's. ' Plants grow, and in 

 growing they produce various metabolic changes and movements of 

 materials. It thus comes about that work of various kinds is performed 

 in living plants, and this necessitates the consumption of energy. . . . 

 The processes of living plants in which organic reserve substances are 

 oxidised by oxygen are quite analogous to combustion, and this vital 

 oxidation is known as respiration.' Kostychev regarded respiration as 

 yielding the necessary release of energy for important vital processes, 

 and he pointed out that ' most syntheses of organic substances, such as 

 the synthesis of proteins,' and ' the various types of architectural pro- 

 cesses of tissue differentiation ' require a supply of energy, although it 

 must be admitted that what exactly he meant by the latter group of 

 processes which, as far as energy requirements were concerned, were not 

 included in the former, is not obvious. At any rate it is quite clear that 

 the general view of respiration, put in as precise terms as possible, is 

 that it provides energy for certain plant movements, and for the building 

 up of substances of higher energy content than the products of photo- 

 synthesis which serve as the substrate. 



While it is not clear that all plant movements obtain the necessary 

 energy for their occurrence from respiratory activity, no doubt some do, 

 and there is every reason to believe that the energy required for the pro- 

 duction of various constituents of the plant arises from the same process. 

 But having agreed to this, can we really be satisfied that we have obtained 

 a complete explanation of the function of respiration ? In the case of 

 germinating seeds, growing organs, the formation of flowers and fruit, 

 this view seems completely adequate, but we must remember that storage 

 tissues such as potato tubers and carrot roots respire at a by no means 

 negligible rate, and that the same is true of senescent organs such as 

 mature fruit. Indeed, such tissues, notably those of the apple, have 

 provided some of the most interesting data of plant respiration. With 

 what movement, or with what synthesis of materials, is respiration of the 

 cells of a mature apple concerned ? Such considerations lead one to 

 wonder whether respiration is not concerned in some much more subtle 

 way with the maintenance of life. It does look as if the mere maintenance 

 of the protoplasm in a living condition depends on the continuous occur- 

 rence of these processes which manifest themselves in the oxidation of 

 organic material to carbon dioxide and water by means of absorbed- 

 oxygen. The only exception to this rule is found in certain so-called 

 ' resting ' organs, such as seeds, in which the amount of water present is 

 very low, and in which, presumably, the protoplasm is in some very 

 different state from that of active cells. 



