A generalized linear model to predict the growth of potted seedlings of satsuma mandarin (Citrus unshiu Marcow.) under different initial plant conditions, environmental conditions, and pot size

To predict the seasonal vegetative growth of potted seedlings of Satsuma mandarin, the effects of initial plant conditions (age, shoot pruning), environment (greenhouse, greenhouse + shading, open-field culture), and pot size on growth were researched for 1.5–2.5 years. The growth pattern was evaluated using a curve fitting with the 4-parameter logistic (4L) model, biomass allocation, and classical (interval) growth analysis, and a generalized linear model analysis based on thermal time (tt). Growth delays from shoot pruning were confirmed by growth trajectories with the 4L model based on tt. Plant growth was positively affected by enlarging the pot size (from 20-L to 45-L), while shading significantly suppressed the growth of 45-L potted Satsuma mandarin seedlings in the greenhouse. In the growth analysis, the relative growth rate was not always determined by the net assimilation rate (NAR), which included both shoot-pruning and pot size effects. To predict the plant mass of Satsuma mandarin seedlings (M _P ), we proposed several generalized linear models using a log link function assuming that M _P followed a Gamma-distribution. The best model to predict M _P was selected based on Akaike information criterion (AIC) values, and contained explanatory variables for initial plant biomass, NAR, specific leaf area (SLA), leaf mass ratio (LMR), pot size, and tt. Some simpler models excluding NAR, but including SLA and/or LMR as explanatory variables, were more useful than a model lacking growth analysis parameters (NAR, SLA, and LMR).