Seasonal changes in nitrate use by three woody species: the importance of the leaf-expansion period

Abstract

Seasonal changes in plant NO 3 --N use were investigated by measuring leaf nitrate reductase activity (NRA), leaf N concentration, and leaf expansion in one evergreen woody species (Quercus glauca Thunb.) and two deciduous woody species [Acer palmatum Thunb. and Zelkova serrata (Thunb.) Makino]. Leaf N concentration was highest at the beginning of leaf expansion and decreased during the expansion process to a steady state at the point of full leaf expansion in all species. The leaf NRA of all species was very low at the beginning of leaf expansion, followed by a rapid increase and subsequent decrease. The highest leaf NRA was observed in the middle of the leaf-expansion period, and the lowest leaf NRA occurred in summer for all species. Significant positive correlations were detected between leaf NRA and leaf expansion rates, while leaf N concentrations were negatively correlated with leaf area. In the evergreen Q. glauca, the N concentration in current buds increased before leaves opened; concurrently, the N concentration in 1-year-old leaves decreased by 25%. Our results show that the leafexpansion period is the most important period for NO 3 --N assimilation by broadleaf tree species, and that decreases in leaf N concentration through the leaf-expansion period are at least partly compensated for by newly assimilated NO 3 --N in current leaves.

Seasonal variation in ammonia compensation point and nitrogen pools in beech leaves (Fagus sylvatica)

“…7), indicating a high proportion of structurally related protein in young leaves prior to the increase in soluble protein, primarily rubisco, during later growth stages. The high levels of NH 4 + may partially have been due to high nitrate reductase activity as the activity of this enzyme has been reported to peak before leaf establishment in deciduous tree (Koyama et al 2008).…”

Lower photorespiration in elevated CO2 reduces leaf N concentrations in mature Eucalyptus trees in the field

“…Demand for N from the photosynthetic apparatus is often associated with the developmental stage of leaves (Hikosaka, ; Koyama, Tokuchi, Fukushima, Terai, & Yamamoto, ; Niinemets, ). Young leaves generally require high N concentrations to build up the photosynthetic and pigment machinery, and hence during development, they constitute a significant sink for this macronutrient to sustain leaf growth and photosynthetic activity (Hikosaka, ; Niinemets, ; Reich, Walters, & Ellsworth, ), an effect that may be intensified in eCO 2 (Hungate, Dukes, Shaw, Luo, & Field, ; Luo, Hui, & Zhang, ).…”

“…Young leaves generally require high N concentrations to build up the photosynthetic and pigment machinery, and hence during development, they constitute a significant sink for this macronutrient to sustain leaf growth and photosynthetic activity (Hikosaka, ; Niinemets, ; Reich, Walters, & Ellsworth, ), an effect that may be intensified in eCO 2 (Hungate, Dukes, Shaw, Luo, & Field, ; Luo, Hui, & Zhang, ). Leaf N concentrations subsequently decline with ageing (Crous & Ellsworth, ; Hikosaka, ; Koyama et al, ; Niinemets, ; Reich et al, ). Thus, leaf developmental age is important to consider when examining leaf N concentrations in eCO 2 .…”

Estimation of leaf nitrogen concentrations in Quercus robur L. using the CCM-200 portable chlorophyll meter for different patterns of vegetative growth and acorn production

“…In deciduous trees, it is mainly the mobile N fraction that is intensively translocated from leaves, resulting in changes in stable/mobile N ratios toward the end of the growing season (Onoda et al 2004;Takashima et al 2004;Ueda et al 2011). As a result, the total N content in leaves gradually decreases and becomes stable toward the end of the growing season (Migita et al 2007;Koyama et al 2008). For this reason, the stable N fraction represents the majority of the LNC by the end of a growing season (Ueda et al 2011).…”