Effect of plant population density on growth and dry-matter partitioning of pineapple

To examine the effect of plant population density (density) on the growth and dry-matter partitioning, 'Smooth Cayenne' pineapple crowns were planted at 2.61, 5.22, 7.83, 10.06, and 12.81 plants m(-2) on June 15, August 15, and October 18, 1989, at Kunia, Hawaii. Flowering of all plantings was forced with ethephon on September 18, 1990. Leaf area and weight of leaf, stem, peduncle, and fruit were periodically recorded. Mean dry weight per plant was greatest for the June planting and decreased in all plantings with increasing density. Relative growth rate (RGR) decreased linearly from about 8.5 to 6.0 g kg(-1) day(-1) as density increased; this was attributed to decreasing net assimilation rate of the canopy associated with intense mutual shading. About 87% of the above-ground dry matter was partitioned to leaves and 13% to stem during vegetative growth, this fraction being not significantly affected by density or planting date. After forcing, most above-ground dry matter was partitioned to the developing inflorescence and stem. The fruit weight : plant weight ratio was unaffected by density, so fruit weight was proportional to plant mass at all densities. As density increased, the proportion of above-ground dry matter partitioned to the stem decreased while that partitioned to fruit increased. We conclude that the fruit is a stronger sink than the stem when assimilate is in short supply due to interplant competition.