Lipid Labeling in Normal and Nitrogen‐Deficient Squash (Cucurbita maxima) Leaves

Squash ( Cucurbita maxima Duchesne) plants were grown on normal and on nitrogen‐deficient nutrients. The degrees of label incorporation into chloroplast lipids as well as non‐chloroplast lipids were determined. Nitrogen‐deficient tissues contain less chlorophyll, have a decreased chlorophyll a/b ratio, incorporate more label into phosphatidyl choline and phosphatidyl ethanolamine than into the chloroplast lipids such as mono‐ and digalactosyl diglycerides, have a reduced capacity to incorporate the hexose moieties into the glycolipids but normal capacity to incorporate bases into the phospholipids of non‐chloroplast constituents, and have a normal level of total fatty acids even though the level of linolenate is decreased. All of this would suggest that the most evident changes in membrane lipid constituents during nitrogen‐deficiency occur as changes in the chloroplast lipid constituents as opposed to the non‐chloroplast lipid constituents.