Resumo

OROZCO-VIDAL, Jorge A. et al. Nitrogen Rate and its Effect on Biomass Production and Distribution of Transgenic Cotton. Terra Latinoam [online]. 2008, vol.26, n.1, pp.29-35. ISSN 2395-8030.

The objective of this work was to study growth indicators and the effect of nitrogen (N) rate on biomass production and distribution of the transgenic cotton (Gossypium hirsutum L.) variety NuCot 35B. N rates were 0, 80, and 160 kg ha^-1. A complete randomized block design with six replications was used. Planting was done in the narrow-row cotton production system (rows 0.76 mapart). Adistance of 0.20 m betweenplants resulted in a population density of 65 500 plants ha^-1. Four destructive samplings were performed 69, 82, 105, and 124 days after planting (DAP). Plant leaf area, total dry weight, and dry weight of plant and reproductive organs from two plants per plot were measured on each sampling date. Total dry weight and plant leaf area data were used to estimate crop growth rate (CGR), net assimilation rate (NAR), leaf area index (LAI), leaf area ratio (LAR), specific leaf area (SLA), and leaf weight ratio (LWR). N rate did not affect total biomass production, biomass partitioning, photosynthetic apparatus size indicators, nor photosynthetic efficiency of the variety studied. At 124 DAP, 60% of the total plant dry weight was accumulated in the reproductive organs. The highest CGR (22.1 g m^-2 d^-1) was observed between 69 and 105 DAP. N rate did not affect the LAR, SLA, and LWR estimator which means that, in all growth phases, the plants accumulated the same quantity of photoassimilates in their leaf sheet. According to LWR, and independently of N rate, plants assigned the same percentage of photoassimilates to their respective foliar structure.

Palavras-chave : Gossypium hirsutum L.; dry matter; growth rate; net assimilation rate; leaf area index.

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