Mean residence time of leaf number, area, mass, and nitrogen in canopy photosynthesis

Abstract

Mean residence time (MRT) of plant nitrogen (N), which is an indicator of the expected length of time N newly taken up is retained before being lost, is an important component in plant nitrogen use. Here we extend the concept MRT to cover such variables as leaf number, leaf area, leaf dry mass, and nitrogen in the canopy. MRT was calculated from leaf duration (i.e., time integral of standing amount) divided by the total production of leaf variables. We determined MRT in a Xanthium canadense stand established with high or low N availability. The MRT of leaf number may imply longevity of leaves in the canopy. We found that the MRT of leaf area and dry mass were shorter than that of leaf number, while the MRT of leaf N was longer. The relatively longer MRT of leaf N was due to N resorption before leaf shedding. The MRT of all variables was longer at low N availability. Leaf productivity is the rate of canopy photosynthesis per unit amount of leaf variables, and multiplication of leaf productivity by MRT gives the leaf photosynthetic efficiency (canopy photosynthesis per unit production of leaf variables). The photosynthetic efficiency of leaf number implies the lifetime carbon gain of a leaf in the canopy. The analysis of plant-level N use efficiency by evaluating the N productivity and MRT is a well-established approach. Extension of these concepts to leaf number, area, mass, and N in the canopy will clarify the underlying logic in the study of leaf life span, leaf area development, and dry mass and N use in canopy photosynthesis.

Physiological evaluation of nitrogen use efficiency and yield attributes in rice (Oryza sativaL.) genotypes under different nitrogen levels

“…An increase in the LAI was reported in response to the N fertilizer application thereby suggesting an increase in the yield of the rice plants. Similarly, high LAI in response to high N application has been reported by Hirose and Oikawa (2012). In present investigation, total chlorophyll content was found to be higher in response to all the treatments of N, which was found in accordance with Li et al (2012) who showed that in rice seedlings chlorophyll content decreased by 8% when fed with low N and increased by 12% when fed with high N. Very close link between chlorophyll and N content has been proved earlier by Amaliotis et al (2004).…”

Leaf dynamics in growth and reproduction ofXanthium canadenseas influenced by stand density

“…The concept of MRT ( Hirose, 2011 , 2012 ) was employed for the analysis of leaf dynamics. Definition and calculation for MRT and related variables of leaf number, area, mass and N followed Hirose and Oikawa (2012) . First, leaf duration (LD i , [i]d) in the period [0, T ] is calculated: where f i ( t ) and g i ( t ) are the leaf production and loss at time t , respectively, both accumulated from the date of transplanting ( t = 0) when no true leaf emerged.…”

“… Hirose and Oikawa (2012) demonstrated that mean residence time (MRT, d) defined for leaf number, area, dry mass and N (collectively ‘leaf variables’) was useful for the study of leaf dynamics. The concept of MRT was introduced earlier as one of the two factors comprising plant N use efficiency (NUE, g g −1 N; Berendse and Aerts, 1987 ) and defined as the expected length of time plant N is retained in the plant body before being lost.…”

“…Mean residence time of leaf N is the expected length of time a unit N newly allocated to the leaf is retained before being lost. Hirose and Oikawa (2012) extended this concept of MRT to cover leaf number, area and mass. MRT calculated for leaf number is the expected length of time a newly born leaf is retained until abscission, implying leaf longevity.…”

Leaf Gas Exchange, Photon Capture and Light Harvest in Aldina heterophylla along a Vegetation Gradient in the Amazon Rainforest

“…The total nitrogen concentration in soil has traditionally been reported as the main factor in biomass accumulation because it increases photosynthesis as a large fraction of the leaf nitrogen is invested in the photosynthetic apparatus and leaf nitrogen contents reflect the amounts of photosynthetic proteins [10] [11]. In general, the growth of plants at higher irradiance and nitrogen availabilities includes a higher net photosynthesis and nitrogen leaf concentration [12].…”