Vergara - 1976 - Physiological and morphological adaptability of ri

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1. Distribution of rice roots among tillers of diflerent orders (lwatsuki. 1932)
Many attempts have been made to classify} the roots of lowland rice in relation
to the aerial parts or tirgans. For example. Iwatsuki (1932) classified the rice
roots on the basis of tillering order. as illustrated in Fig. l. It is evident that the
later the tillering order, the fewer the roots initiated.
An excellent theory on the emergence of rice roots was proposed by liugiii
(1961) who conducted extensive utork along Katayamas (1951) theory: on
tillcring of cereal crops. Focusing his attention on the periodicity of emergence
and synchronized elongation of leaves and roots in lowland rice. Fujii revealed
that 5 to 23 roots emerged and elongated simultaneously from a certain node
when a leaf blade from the upper third node elongated. That is, synchronized
elongation was observed between the nodal roots of a certain node and the
lamina of the upper third node in lowland rice. ln other Words, when the nth
leaf blade began to elongate. the (n-3)th nodal roots also began to elongate
together with the (n-3)th tiller. because the n-th lantina and (n-3)th tiller show
synchronized elongation. according to Katayama (1951).
Fujii (1961) found that the regularity of nodal root emergence in a rice plant
was similarly maintained in tillers. A delay of l5 to 20 days in the increase of
number of roots compared with that of tillers. which was observed by Sato
(1937) and tithers, tvas explained by the observation that roots are initiated on a
tiller when it has at least three leaves. Iwatsukrs (I932) observation that the
higher tillers bore fewer roots might be explained by the decreasing number of
leaves that emerged. Subsequently studying the emergence of lateral. secondary.
and tertiary roots. along the same line as mentioned above. Fujii (1961) found
that the emergence of secondary roots was synchronized with that of the leaf
blade of the upper fourth node. and that of tertiary roots with that of the fifth.