PLASTOGLOBULI OF SPINACH - THEIR SIZE AND COMPOSITION DURING CHLOROPLAST DEGENERATION

1. During degeneration of spinach chloroplasts in senescent leaves both thylakoids and plastid-stroma are dissolved progressively. The osmiophilic plastoglobuli remain, however. Their size increases during degeneration until the early yellow stage of the spinach leaves (size range 80-300 nm, average diameter 165 nm). Their frequency does not increase. In the final yellow stage of spinach leaves occur some larger plastoglobuli (diameter 300-700 nm) which arise by fusion of smaller ones. 2. During breakdown of chlorophylls and thylakoids the level of xanthophylls and vitamin K1 remain approximately the same, while -carotin is partly destroyed. The plastidquinones of the benzoquinone type (plastoquinone 45, α-tocopherol and α-tocoquinone) are still synthesized, mainly, however, α-tocopherol. 3. Those lamellar chloroplast lipids, which are not destroyed on thylakoid breakdown like carotenoids and plastidquinones are deposited in the osmiophilic plastoglobuli, whose size thus increases. The plastoglobuli isolated from degenerating spinach chloroplasts possess a higher carotenoid portion than do plastoglobuli from fully functional chloroplasts. © 1969 Springer-Verlag.