Growth analysis of potted seedlings of satsuma mandarin (Citrus unshiu Marc.) under different light conditions and air temperatures
2018
Yano, T. (Oita Prefectural Agriculture, Forestry and Fisheries Research Center, Kunisaki (Japan)) | Morisaki, A. | Matsubara, K. | Ito, S. | Kitano, M.
To establish cultural practice based on a consecutive growth model for potted 1-year-old seedlings of Satsuma mandarin (Citrus unshiu Marc.), growth analysis by classical and functional approaches was conducted under different light conditions and air temperatures over 2.5 years, and the active growth of potted seedlings in the greenhouse was investigated. Under the classical approach, the general change patterns of relative growth rate (RGR) and net assimilation rate (NAR) were hard to determine because of irregularities including quiescence of vegetative growth. Under the functional approach, plant mass modeled using linear, exponential, power-law, monomolecular, three-parameter logistic, four-parameter logistic (4L), and Gompertz functions showed significant correlations with the observed plant mass. 4L was the best model because it showed the highest r, and the lowest root mean square error and Akaike Information Criterion, so RGR and NAR were estimated by 4L. Analysis of the RGR components showed significant positive correlations between RGR and NAR. Analysis of covariance indicated the NAR costs for increasing RGR were lower in the greenhouse than in open culture; this was explained by differences in specific leaf area (SLA). Therefore, in greenhouse culture, growth was primarily enhanced by NAR as net photosynthesis and underpinned by SLA as a morphological trait improvement for the relatively low light intensity compared with open culture. A multiple regression model for NAR using the pooled data (n = 60) suggested solar radiation had a positive effect (P < 0.0001) and air temperature had a negative effect (P < 0.01) on NAR.
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