パイナップルの物質生産に関する研究(乾物生産と収量成立過程について)

Abstract

Dry matter production in pineapple plants which were transplanted to the field in September could be divided into four stages: 1) the first stage of early plant growth; 2) the second stage of middle plant growth; 3) the third stage of fruitlet differentiation; 4) the fourth stage of fruitlet growth. These stages were strongly affected by the climate of the season.At harvest, the total dry weight per plant of ‘Mitsubishi’ was heavier than that of ‘Hawaii’. However, the dry weight of the fruit was lower. This shows that translocation of photosynthates to the fruit was more active in ‘Hawaii’ than in ‘Mitsubishi’.Leaf area index (LAI) increased rapidly in the latter half of the second stage and reached a maximum of 6.5 in the third stage. The maximum value remained almost unchanged until the fourth stage.Seasonal changes of the crop growth rate (CGR) showed bimodal curves with two peaks. The first peak appeared in the second stage (October) and the second one in the fourth stage from May to June. The maximum CGR was 8.1-8.2gm-2Net assimilation rate (NAR) were similar to those of CGR. Maximum NAR was observed in the second stage (August) and the value was 2.40 to 2.55gm-2 day-1. NAR was largest when the LAI was 2 to 3. CGR reached a maximum when LAI was 3 to 4. Optimum LAI was estimated to be 3.01.Relative growth rate (RGR) was closely correlated with NAR. Efficiency of solar energy utilization was 0.2% in the first stage and reached a maximum of 1.2% in December. Flower bud initiation began from this time.Active accumulation of photosynthates in the fruit was observed when LAI was kept at 3.01 and when flower bud induction treatment was practiced. Analyses of dry matter production of pineapple plants and the structure of the community showed that to achieve a short leaf length and narrow angle of leaf emergence were necessary community with high productivity. Thus, breeding should be carried out to select plants with these characteristics.