Tp. Rao et O. Ito, DIFFERENCES IN ROOT-SYSTEM MORPHOLOGY AND ROOT RESPIRATION IN RELATION TO NITROGEN UPTAKE AMONG 6 CROP SPECIES, JARQ. Japan Agricultural Research Quarterly, 32(2), 1998, pp. 97-103
Cereals and legumes that originated from the semi-arid tropics (SAT) a
re mainly grown in marginal soils with limited water and nutrient reso
urces. Initial root system development is crucial for crop establishme
nt in order to acquire these minimal resources. A comparative study of
the root system morphology and of some physiological parameters at in
itial growth stages was carried out for 3 legumes: pigeonpea, chickpea
and groundnut, and 3 cereals: sorghum, pearl millet and maize, the co
mponent crops of the semi-arid tropics. Considerable differences were
observed for all the root morphological traits among the species. Amon
g the legumes, chickpea produced few thick and lengthy laterals, while
pigeonpea produced a high frequency of thinner laterals. However grou
ndnut had a larger root system than the other 2 legumes. Among the cer
eals, maize formed a large root system followed by sorghum with a high
frequency of laterals, while millet displayed a smaller root system w
ith thin roots. The root respiration rate was significantly correlated
with the N uptake activity. The legumes showed a higher efficiency of
N uptake in terms of respiratory requirement. The transpiration rate
showed a significant correlation with total N concentration in shoot,
indicating that transpiration may be partly related to nitrogen flow t
o and accumulation in shoot in case of nitrate nitrogen as a sole nitr
ogen source. Morphological and physiological characters of the root sy
stem using rather simple indices were found to be better criteria for
describing functional differences among crop species.