Abstract
The ecophysiological parameters of coffee canopy were mapped throughout the day. Therefore, evaluations were carried out in ‘Catuaí Vermelho’<em> Coffea arabica</em> L., measuring 1.7 meters. A vertical gradient (from the apex to the base of the plant canopy) and a horizontal gradient (plagiotropic branches) were established to analyze different positions of the canopy. Thus, in the vertical direction, four heights were analyzed in the plant: top, upper, middle and lower regions. In the horizontal gradient, the plagiotropic branches were divided into three parts: basal, median and apical. Collection was performed on the east and west sides of the canopy, at four times of the day: 6 a.m., 9 a.m., noon, and 3 p.m., totaling 24 collection points at each time. Gas exchange, photosynthetically active radiation and leaf temperature were evaluated in each of the 24 points of the coffee canopy. The gas exchange characteristics of an individual coffee leaf diverge considerably from other leaves, which require caution when scaling estimates of leaf photosynthesis at the global canopy level. The analysis of some punctual leaves does not serve to discriminate the overall dynamics of a canopy.
Highlights
The coffee tree canopy acquires a dynamism during its development, being modified by environmental conditions, physical structure, age and type of leaves (RODRÍGUEZ et al, 2011), besides the distribution and translocation of photoassimilates among different parts and heights of the plant
Higher A rates were obtained at 9 a.m. and noon at the eastern side of the plant canopy (Figure 2A, B, C)
Considering the vertical gradient, net photosynthetic rate varied in response to the time of the day: at 6 a.m., higher values occurred at the eastern side of the plant; at 9 a.m., it was concentrated at the top and upper branches; at noon, the lower branches showed higher A and, at 3 p.m., leaves from the top of the canopy showed the highest net photosynthetic rates (Figure 2D)
Summary
The coffee tree canopy acquires a dynamism during its development, being modified by environmental conditions, physical structure, age and type of leaves (sun and shade leaves) (RODRÍGUEZ et al, 2011), besides the distribution and translocation of photoassimilates among different parts and heights of the plant. In this sense, inside the canopy, there are variations in the interception of solar radiation, interception of rainfall through foliage layers, wind speed, air temperature, canopy temperature, humidity, CO2 availability, nitrogen partitioning, pigment content, vapor pressure deficit and cell metabolism (CAMARGO, 2010). The net photosynthetic rate of shaded leaves seems to be more limited by the low light availability for leaves than by stomatal conductance
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