Studies in the Root and Shoot Growth of the Strawberry

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Abstract
Development of the runner and the root system is described. Adventitious roots arise from small groups of meristematic cells within the stele, alternating with the primary vascular strands and between the outer pericycle tissue and the medullary tissues of the center of the stele. These groups are observed in greatest number in the region of departure of the leaf-trace bundles. Differentiation of the apical meristem of the root occurs before the differentiation of the secondary vascular cambium of the stem in the majority of cases, differing in this respect from that recorded in other plants. The initiation of root meristems in the stem occurs during periods of vigorous growth, characterized by the absence of excess carbohydrates and a low dry matter content of the tissues. Further development of the roots follows on a period of carbohydrate accumulation as indicated by deposition of starch in the storage parenchyma of the plant as a whole, and a marked increase in dry matter content. When vigorous growth of the shoot occurs simultaneously with a readily available supply of carbohydrate materials, as in the case of the young "runner" plant, further development of root meristems follows closely on their initiation. The development of a specialized polyderm forms a very characteristic feature of the older main roots, which continue to develop secondary tissues and function little as absorbing organs after their first season''s growth. No polyderm development was observed on the majority of the lateral roots and they became largely functionless with the formation of new adventitious roots in the later summer and autumn. In the primary condition of the root, starch accumulates in the cortex; in roots showing secondary developments of phellogen and vascular tissues, the phelloid cells of the polyderm form the chief region of starch deposition. Accumulation occurs as the dormant season is approached, and again during the month of June and in early July. Depletion takes place in the spring and in late July, during periods of vigorous new root development.

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