In this article:
The frequency and duration of sunflecks (= I cm2) were recorded in the vineyard.
These patterns were then simulated on single leaves in the laboratory and photosynthetic responses were measured. Average duration of sunflecks was 0.6 seconds and they were spaced at a mean interval of 1.2 seconds. Intermittent or alternating light cycles at this periodicity were used with maximum effectiveness for photosynthesis.
The ecological significance of sunflecks is discussed in relation to sunfleck utilisation by leaves deep inside the vine canopy where the level of diffuse radiation can be close to compensation point and respiratory losses from an entire leaf are apparently offset by irradiating up to 1% of its area with light flecks of saturating density of radiant flux.
Natural Occurrence and Photosynthetic Utilisation of Sunflecks by Grapevine Leaves
1973, Photosynthetica, vol 7, issue 1, pages 18 – 27
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