Vergara - 1976 - Physiological and morphological adaptability of ri

cntnyrn AND NUTRIENT LIPTAKE or RICE Roors 267
Fujifs ( 1961) work broadened the scope of root studies of lowland rice. It
presented a comprehensive theory on the emergence and elongation of roots
that has hitherto been regarded as extremely complicated. At the same time, he
established a morphological basis for the interpretation of tl1e interrelation and
interdependence between aerial and underground organs.
From a similar point of vie w, Inosaka (1962) who investigated the branching,
connection, and development of vascular bundles in lowland rice, stressed the
importance of nodes in the formation of roots and aerial organs.
Kawata et al. (I963), following the work of Fujii (1961) and lnosaka (1962).
carried out a detailed survey on the formation of root systems of lowland rice
grown in a paddy field. They added new discoveries to the theory ofFujii (1961)
and constructed a unique theory They claimed that Fujifs theory was defective
in that it combined the two rows of roots that emerged above and below a node
and regarded them as nodal roots of the said node. Kaivata et al. (1963) thought
it more reasonable to assume a"shor1 unit," a concept similar to the “leafintemode
unit" presented by Shannan (1941) in corn, as the fundamental growth
unit of rice (Fig. 2). because comparatively thin roots emerging below a node
elongate simultaneously with the thick roots that emerge in the upper region of
the adjacent lower node. Upper and lower roots of a shoot unit, however, show
some differences in morphological features; the upper roots. usually thinner than
the lower ones, tend to extend horizontally or obliquely‘ upwards. distributing
densely in the upper and middle lafrer of furrow soil. As a result. a superficial
root mat develops at the surface of paddy soil. which plays an important role in
upper
roots
Sh»! llit
Kuuutu e1 alt 9N)
fillt
m" '99" Cmh-structrn unit
lshinlfl 8 Ttlflllill I963]
2. Diagrammatic representation of unit concept.