Canopy Architecture and Leaf Nitrogen Distribution of Rice (Oryza sativa L.) under Chronic Soil Water Deficit

Abstract

The development of vertical gradients of specific leaf nitrogen (SLN) in accordance with light gradients within a canopy is important for maximising resource‐use efficiency. In this study, we aimed to clarify the effect of chronic soil water deficit on the SLN gradient in rice. In a series of field experiments, SLN gradients of an indica cultivar and a tropical japonica cultivar were investigated under chronic soil water deficit. As a result, SLN gradient of an indica cultivar tended to be more uniform than that of a tropical japonica cultivar during the recovery period after dry spells under aerobic conditions: an indica cultivar distributed much N in shaded leaves while a japonica cultivar enhanced the SLN in the upper layers. We conclude that vertical gradient of SLN of indica cultivars becomes less optimal for photo‐assimilation under chronic soil water deficit, although they can take‐up sufficient amounts of N. This would be attributable to the rapid increase in tiller number upon rainfall or irrigation and prolonged tillering period for their recovery growth, leading to a more compact canopy architecture. The tillering habit in the current indica irrigated rice cultivars would be associated with the response of SLN gradients to chronic soil water deficit.

Identification and characterization of high‐yielding, short‐duration rice genotypes for tropical Asia

“…Reduced resource allocation to elongating internodes during the reproductive stage led to less competition between organs for nonstructural carbohydrates, thereby enabling larger panicle size in semidwarf varieties (Kato et al., 2014). Simultaneously, the canopy structure of these varieties has been modified to lower the light extinction coefficient (i.e., by producing more upright leaves and tillers), which has contributed to greater biomass accumulation during the grain‐filling stage (Okami, Kato, & Yamagishi, 2016; Peng et al., 2008). However, breeders of short‐duration varieties should modify plant development to increase the current level of LAI during the limited period of vegetative growth.…”

Assessing the Effects of Water Deficit on Photosynthesis Using Parameters Derived from Measurements of Leaf Gas Exchange and of Chlorophyll a Fluorescence

“…There is some evidence that WD may accelerate loss of leaf nitrogen and chlorophyll, and enhance senescence as it was observed in wheat (Yang et al, 2001 ). Recently, Okami et al ( 2016 ) observed that the optimal vertical distribution of leaf nitrogen content expressed on leaf mass basis, N m , may be affected by drought in an indica cultivar of rice. But generally it takes severe stress before the structure, not purely the functioning, of the photosynthetic machinery is affected.…”

Vertical profile of photosynthetic CO₂ response within rice canopy

“…The potential photosynthetic capacity of rice leaf was highly related to leaf nitrogen content (Xu et al 2014, Yang et al 2016, and Vcmax, Jmax, and Vp markedly increased with an increasing leaf nitrogen content (Nakano et al 1997, Yin et al 2009, Gu et al 2012. Moreover, the leaf nitrogen content was low for the upper new-emerged and unexpanded leaf and usually decreased from the top to the bottom of rice canopy for the fully expanded leaf (Yang et al 2014, Okami et al 2016, which indicated the patterns of Vcmax, Jmax, and Vp in Fig. 3A-C.…”