Field Crops Research 186 (2016) 117–123 Contents lists available at ScienceDirect Field Crops Research jou rn al hom epage: www.elsevier.com/locate/fcr Parameterization of leaf growth in rice (Oryza sativa L.) utilizing a plant canopy analyzer Yoshihiro Hirooka a , Koki Homma a,b,∗ , Tatsuhiko Shiraiwa a , Mitsuo Kuwada a,c a Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502, Japan b Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi, Aoba, Sendai 981-8555, Japan c NPO Nonorganic, Nonchemical Crop Production Research Group, Yoshida-Kaguraoka, Sakyo, Kyoto 606-8311, Japan a r t i c l e i n f o Article history: Received 3 August 2015 Received in revised form 7 November 2015 Accepted 9 November 2015 Keywords: Dynamics of leaf growth Frequent measurement Mathematical growth model Parameterizing leaf growth a b s t r a c t Monitoring leaf growth is a useful method for evaluating crop growth. In this study, frequent measure- ments of the rice canopy were conducted with a plant canopy analyzer, and parameters were estimated by applying several equations to evaluate leaf growth. The applicability of this evaluation method is dis- cussed based on the statistical analysis of parameters. Experiments were conducted for 6 rice cultivars under 5 treatments in 2 years. Parameters describing the dynamics of leaf growth were obtained by applying 4 mathematical growth models in which the independent variable was the effective accumu- lated temperature. The parameters numerically represented the dynamics of leaf growth in each cultivar and treatment. In particular, maximum LAI and interception growth rates (MLGR and MIGR) which were obtained by applying logistic function to leaf area index (LAI) and diffuse non-light intercepted (DIFN), respectively, showed no interaction between the cultivar and environment. The lack of interaction may indicate that these parameters typically characterize cultivar and growth environments. The differences in the parameters could also be used to quantify the effect of basal fertilizer application on leaf growth enhancement and that of additional fertilizer on the extension of this enhancement. These results suggest that the applied method for parameterizing leaf growth based on frequent measurements with a canopy analyzer is suitable for evaluating the effects of genotype, management and the environment because it facilitates measurements in many plots. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The efficiency of light capture primarily restricts crop produc- tion. Because the efficiency of light capture is primarily determined by leaf growth, monitoring leaf growth is a useful method for eval- uating crop growth (Maki and Homma, 2014). The leaf area index (LAI) is a key ecological and biophysical parameter related to leaf growth (GCOS, 2011), and the LAI of rice is different among different cultivars and growth environments (Yoshida et al., 2007; Setiyono et al., 2008). The relative growth rate and maximum growth rate are representative parameters of LAI dynamics (Milthorpe and Moorby, Abbreviations: LAI, leaf area index; DIFN, diffuse non-light intercepted; RGR, rel- ative LAI growth rate; LGR, leaf growth rate; MLAI, maximum LAI; MLGR, maximum LAI growth rate; MIGR, maximum interception growth rate; iLAIexp, initial LAI at transplanting estimated by exponential function; iLAI log , initial LAI at transplanting estimated by logistic function. ∗ Corresponding author. E-mail address: koki.homma.d6@tohoku.ac.jp (K. Homma). 1979; Lizasoa et al., 2003), and these parameters may therefore also represent the effect of cultivars and environments on leaf growth. The methods for performing in situ LAI measurements can be grouped in two main categories (Dovermann and Pampolino, 1995; Jonckheere et al., 2004; Weiss et al., 2004): destructive and non-destructive. Destructive measurement methods involve cut- ting green leaf blades from plant samples and measure leaf area with an area meter. However, these methods present the disadvan- tage of requiring relatively laborious work to collect and measure the samples. Alternatively, non-destructive measurement methods employing plant canopy analyzers such as the LAI-2000 (LI-COR, Inc., Lincoln, NE; LI-COR, 1989, 1992) and SunScan (Delta-T Devices, Cambridge, UK; Potter et al., 1996) instruments can be utilized to overcome the disadvantages of destructive measurement methods. The LAI-2000 is one of the most widely used optical instruments. Researchers have reported indirect measurements of LAI obtained with the LAI-2000 in common bean (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.] (Hicks and Lascano, 1995; Dingkuhn et al., 1999; Wilhelm et al., 2000; de Jesus et al., 2001; http://dx.doi.org/10.1016/j.fcr.2015.11.002 0378-4290/© 2015 Elsevier B.V. All rights reserved.