Characterization of Root Systems with Respect to Morphological Traits and Nitrogen-Absorbing Ability in the New Plant Type of Tropical Rice Lines

Abstract

The objective of this study was to characterize the root systems of the new plant type (NPT) of tropical rice (Oryza sative (L)) lines compared with the root system of IR72, one of the elite modern varieties. Two field experiments were conducted to observe plant growth under canopy conditions in the 1997 and 1998 wet seasons. In addition, a pot experiment was conducted in the 1998 dry season to observe plant growth under isolated conditions. The root systems of the NPT lines were characterized by roots heavier than those of IR72. The larger root dry weight (DW) is attributed partly to a genetically determined high root/shoot ratio because, irrespective of growth conditions, the ratio was larger in the NPT lines than in IR72. An increase in root DW was accompanied by an increase in the length of the whole root system, including fine roots. However, despite the differences between the NPT lines and IR72 in root DW and root length, there were no significant differences in the amount of nitrogen (N) absorbed throughout the growth period. Therefore, the specific absorption rate of N per root DW (SAR N , mg N g −1 root DW d −1 ) was lower in the NPT lines than in IR72. We concluded that, although the root systems of the NPT lines grew prolifically, they were not necessarily more efficient in terms of N absorption compared with the root system of IR72.

Performance of a High-Yielding Modern Rice Cultivar Takanari and Several Old and New Cultivars Grown with and without Chemical Fertilizer in a Submerged Paddy Field

“…14). These observations suggest that the characteristics of the root systems in the new cultivars, in particular Takanari, might be attributed to the greater accumulation of nitrogen (Ookawa et al, 2004;San-oh et al, 2006b) although the increase in root dry weight and root length did not result in the promotion in nitrogen absorption in some cultivars (Samejima et al, 2005). This hypothesis remains to be confirmed.…”

Changes in Grain Yield and Root Morphology and Physiology of Mid-Season Rice in the Yangtze River Basin of China During the Last 60 Years

“…What morphological and physiological traits of roots should be for a high-yielding rice cultivar is still debating. Whether or not a larger root biomass and a stronger root activity would contribute to higher grain yield in rice remains an argument (Samejima et al, 2005;Yang et al, 2011). Earlier studies have showed that the rice root number, root weight, and root absorbing area were closely related with grain yield (Zhang et al, 2011(Zhang et al, , 2013Yang et al, 2012).…”

Rice root growth and physiological responses to SRI water management and implications for crop productivity

“…We note here that several researchers have demonstrated that the greater efficiency of hybrid and 'super-rice' varieties is attributable in part to their genetic potential to maintain a higher rate of root oxidizing activity or delayed senescence of roots during later growth stages which translated into higher grain yield (Osaki et al 1997;Samejima et al 2005). Our present study showed, on the other hand, that management practices such as alternative water management and enhanced soil microbial density can also have significant effects on root development and roots' senescence rate, with subsequent impact on yield-influencing parameters.…”