Alternation in Lipid Composition of Wheat Leaves Induced by Phosphate Deficiency Is Related to Both Lipid Biosynthesis and Phosphatidylglycerol Degradation Effects of Membrane Lipids on the Electron Transfer Activity of Cytochrome b6f Complex from Spinach Regulation of Xanthophyll Cycle of Photosystem by Antenna Proteins and Thylakoid Membrane Lipids