Abstract
Abstract Light distribution within canopies is important for plant growth. We aimed to quantify the influence of row orientation on inter- and within-row variation of light absorption and photosynthesis in a hedgerow crop. An experiment with two row orientations of a tomato crop was conducted which was then used to calibrate a functional–structural plant model (FSPM). The FSPM was used to analyse light absorption and photosynthesis for each of the row facing directions in the double-row trellis system (e.g. north- and south-facing rows for the east–west row orientation). The measured leaf area decreased by 18 % and specific leaf area by 10 %, while fruit dry weight increased by 7 % for south-facing compared to north-facing rows, but total plant dry weight did not significantly differ. Model simulations showed a 7 % higher light absorption for the south-facing rows than north-facing rows, while net photosynthesis was surprisingly −4 % lower, due to local light saturation. When in the model leaf area was kept equal between the rows, light absorption for the south-facing rows was 19 % and net photosynthesis 8 % higher than for north-facing rows. We conclude that although south-facing rows would be expected to have a higher photosynthesis than north-facing rows, plants can adapt their morphology such that differences in light absorption and photosynthesis between north- and south-facing rows are minimal. Rows oriented north–south were more uniform in light absorption and photosynthesis than east–west rows, but the overall crop light absorption and photosynthesis were minimally affected (both 3 % lower compared to east–west orientation).
Highlights
Plant positioning in rows causes inter- and intra-row shading, which affects the light distribution and pattern throughout the whole day (Trentacoste et al 2016; Campos et al 2017)
Similar to Trentacoste et al (2016) we found that the biggest differences between north- and south-facing rows are found in the middle layer of the canopy, followed by the top and the bottom of the canopy (Fig. 2)
Despite the higher uniformity when rows were oriented north–south, the overall crop light absorption and photosynthesis were slightly higher for an east–west orientation
Summary
Plant positioning in rows causes inter- and intra-row shading, which affects the light distribution and pattern throughout the whole day (Trentacoste et al 2016; Campos et al 2017). Inter- and intra-row shading have been experimentally studied in relation to weed control (Borger et al 2010; Johnson and Davis 2015; Borger et al 2016) and hedgerow productivity and fruit quality (review by Trentacoste et al 2015). For hedgerow productivity and product quality, a north–south row orientation is often favourable as reviewed by (Trentacoste et al 2015) These authors argued that this is the result of a more equal distribution of light to the most important leaves and fruits between both east- and west-facing parts of the rows during a day in a north–south row orientation. A south-facing side can be lightsaturated, while the north-facing side of a tree is still limited by light, resulting in unequal fruit set (Khemira et al 1993), fruit abortion or
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