Experimental and Analytical Studies of Pteridophytes

Abstract

The relation between the nutrition of the shoot apex and its morphogenetic activity is discussed with special reference to the ferns. From an early stage in the individual development the distal region of the shoot is dependent on supplies of nutrients (the term is used in a comprehensive sense) passed up from the basal absorptive region. The obconical enlargement of the shoot is attended by an increase in the size of the apical and sub-apical regions; but whereas the primary morphogenetic activities of the apical region are closely comparable in small and large apices, very pronounced differences in leaf shape and size and in stelar morphology may be induced according to the nutritional status of the sub-apical regions. Large apices, which normally yield large and complex leaves and an elaborate vascular system, can, by appropriate treatments, be caused to yield 'juvenile' leaves and a simple vascular system. The nutritional status of the sub-apical regions is thus seen to be of considerable interest and importance in studies of morphogenesis. A conception of the mode of distribution of nutrients in the shoot apex is described and discussed. The need for physiological investigations of the apex is emphasized and the scope for new work using the methods of tissue culture is indicated by reference to recent published work.