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AbstractTo assess (after)effects of temperature on plant development, in vitropotato plantlets produced at 17 or 23 °C (normalisation phase, 3 weeks) were planted into soil in growth chambers at 18/12 or 26/20°C (transplant production phase, 2 weeks), and transplanted to glasshouses at 18/12 or 26/20°C (tuber production phase, 6 weeks). The latter phase commonly takes place in the field. Transition from one phase to another, especially from in vitroto in vivoconditions, greatly increased leaf growth and to a smaller extent stem growth. Within a phase, higher temperature stimulated vegetative growth, but delayed tuber formation and reduced tuber yields, harvest index (HI) and tuber dry matter concentration. Temperature during tuber production was more important for high yield than temperatures during earlier phases. Normalisation and transplant production temperatures nevertheless showed after-effects in later phases. Lower normalisation temperatures advanced plant development: they increased vegetative growth in subsequent phases and finally increased fresh tuber yield and HI. This could have yield advantages at locations where field production seasons are short. Lower transplant production temperatures reduced vegetative growth in the next phase, but enhanced early tuber production. Finally they increased tuber dry weight and HI when tuber production temperatures were high. This may increase yield at locations where field conditions delay tuber formation.

AbstractIn vitropropagated potato plantlets, cultivars Gloria and Spunta, were pre-treated with 10 or 40 mg nitrogen per plant before transplanting to the field to determine after-effects of nitrogen on field performance of these transplants in two experiments. Yield, ground cover (GC), accumulated intercepted radiation (AIR), radiation use efficiency (RUE) and harvest index (HI) were assessed. Spunta had higher GC, AIR, total dry matter and tuber fresh and dry weights but lower RUE and HI than Gloria at final harvest. Nitrogen pre-treatment had no clear effect on plant growth at the end of the transplant production phase or during early field growth. Later, higher nitrogen pre-treatment resulted in a slightly higher GC and AIR. In one experiment this resulted in a significantly higher yield. Pre-treatment did not affect HI at the end of the season. Nitrogen pre-treatment can improve seasonal light interception of plantlets of transplant crops from early cultivars.

AbstractAboveground leaf area and leaf number development of in vitroproduced potato plantlets was studied over three growth phases. In vitroplantlets were produced at 17 or 23°C (normalisation phase, 3 weeks), planted in soil at 18/12 or 26/20°C (transplant production phase, 2 weeks), and later transplanted at 18/12 or 26/20°C (tuber production phase, 6 weeks).Boosts in leaf area increase and leaf appearance occurred in the first days after planting to soil. A shock in leaf area increase occurred after the later transplanting. Both for plant averages and most individual plants, leaf area increase in all growth phases was best described by logistic curves, indicating growth limitations occurred in all phases. These limitations were least severe during the relatively short transplant production phase. Higher temperatures did not significantly increase leaf area during normalisation, increased leaf area during transplant production, and first increased but later reduced leaf area during tuber production. Higher temperatures increased leaf number in all phases. After-effects of normalisation temperature occurred during transplant production but no longer during tuber production. After-effects of transplant production temperature occurred during tuber production. After-effects were direct (affecting plants at the beginning of the next phase) or appeared later.

AbstractLeaf area increase of individual, in vitroproduced potato plantlets was analysed over three growth phases: in vitronormalisation (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.

In vitro propagated potato plantlets, cultivars Gloria and Spunta, were pre-treated with 10 or 40 mg nitrogen per plant before transplanting to the field to determine after-effects of nitrogen on field performance of these transplants in two experiments. Yield, ground cover (GC), accumulated intercepted radiation (AIR), radiation use efficiency (RUE) and harvest index (HI) were assessed. Spunta had higher GC, AIR, total dry matter and tuber fresh and dry weights but lower RUE and HI than Gloria at final harvest. Nitrogen pre-treatment had no clear effect on plant growth at the end of the transplant production phase or during early field growth. Later, higher nitrogen pre-treatment resulted in a slightly higher GC and AIR. In one experiment this resulted in a significantly higher yield. Pre-treatment did not affect HI at the end of the season. Nitrogen pre-treatment can improve seasonal light interception of plantlets of transplant crops from early cultivars.

To assess (after)effects of temperature on plant development, in vitro potato plantlets produced at 17 or 23 °C (normalisation phase, 3 weeks) were planted into soil in growth chambers at 18/12 or 26/20°C (transplant production phase, 2 weeks), and transplanted to glasshouses at 18/12 or 26/20°C (tuber production phase, 6 weeks). The latter phase commonly takes place in the field. Transition from one phase to another, especially from in vitro to in vivo conditions, greatly increased leaf growth and to a smaller extent stem growth. Within a phase, higher temperature stimulated vegetative growth, but delayed tuber formation and reduced tuber yields, harvest index (HI) and tuber dry matter concentration. Temperature during tuber production was more important for high yield than temperatures during earlier phases. Normalisation and transplant production temperatures nevertheless showed after-effects in later phases. Lower normalisation temperatures advanced plant development: they increased vegetative growth in subsequent phases and finally increased fresh tuber yield and HI. This could have yield advantages at locations where field production seasons are short. Lower transplant production temperatures reduced vegetative growth in the next phase, but enhanced early tuber production. Finally they increased tuber dry weight and HI when tuber production temperatures were high. This may increase yield at locations where field conditions delay tuber formation.

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).

Aboveground leaf area and leaf number development of in vitro produced potato plantlets was studied over three growth phases. In vitro plantlets were produced at 17 or 23°C (normalisation phase, 3 weeks), planted in soil at 18/12 or 26/20°C (transplant production phase, 2 weeks), and later transplanted at 18/12 or 26/20°C (tuber production phase, 6 weeks).