Quantity Vs. Quality of Sunlight
Many of the fruiting vegetables require full sun (atleast 6 hours of direct sunlight as they define it). However, I was just wondering if the intensity of the sunlight also has any effect on reducing this requirement? In a desert climate of Saudi Arabia - even in October - the sunlight is so intense that the leaves burn if not shaded. I have time and again read that vegetables plants prefer / appreciate shading in desert climates but then this raises the question as to how the sunlight quantity requirements (of atleast 6 hours) gets fulfilled to produce a comparable output with that of more moderate USDA zones (6-7-8)?
Whether this 6 hours requirement is for places where the intensity is moderate or is is applicable to vegetables grown in any climate zone? Can plants growing in desert climate work as good with 4 (or lesser) hours of direct sunlight compared to 6-8 hours of sunlight in more moderate climates? Can the intensity of the sun compensate for the reduced number of hours of direct sunlight? Is there any sort of scientific explanation for this phenomenon?