Abstract
Leaf area increase of individual, in vitro produced potato plantlets was analysed over three growth phases: in vitro normalisation (3 weeks, 17 or 23°C), transplant production (2 weeks, 18/12 or 26/20°C) and tuber production (6 weeks, 18/12 or 26/20°C). In each phase, initial leaf area (ILA) and final leaf area (FLA) of logistically growing plants were related to parameters describing logistic growth (leaf area = A+C/(1+exp(−Bx(t−M))); A: fitted minimum leaf area, B: fitted initial relative rate of increase, C: fitted maximum increment, M: fitted midpoint, MI: maximum rate of increase at M, MI = B×C/4).
Higher ILA was associated with higher FLA during normalisation and transplant production, but not consistently during tuber production. During normalisation, higher ILA led to higher A, C and MI-values, and at 23 °C also to higher B and earlier M. During transplant production, higher ILA was associated with higher C.
During normalisation, leaf area increase of plants with higher FLAs was characterised by higher A, C and MI-values, and at 23°C also by earlier M. During transplant production, higher FLAs were associated with higher C and MI-values, and at 18/12°C also with higher A. During tuber production, higher FLAs were associated with higher C, M and MI-values.
Correlations among parameters characterising logistic growth were of physiological origin, mathematical origin, or resulted from the actual shape of the logistic curve. A and B were positively correlated, likely because clearer S-shaped curves result in higher values of both. Both parameters usually were positively correlated with MI, likely because MI is a function of B, whereas A was correlated to B. Physiologically relevant correlations were found between M and C in the tuber production phase.