Structure and development of plastids in hypsophylls of Euphorbia pulcherrima and Bouganwillea sp.

The fine structure of plastids in hypsophyll at different stages of development and pigmentation has been followed in two short-days plants: Euphorbia pulcherrima and Bouganwillea.In Euphorbia the young chloroplasts observed in the embryonal green hypsophyll change into plastids of small dimensions when contained in the red expanded hypsophyll. Moreover in the green leaves, where red colour is afterwards superimposing, chloroplasts are undergoing a degenerative process. In Bouganwillea the plastid ultrastructure is changing from a young embryonal feature to a moderately developed state, while in the fully expanded hypsophyll degenerated chloroplasts are present together with a population of plastids characterized by numerous large globules and few residual membranes. The unlike chloroplasts behaviour observed in the two different hypsophylls is discussed keeping in consideration pigment synthesis and hypsophyll derivation.In Bouganwillea phloem tubes characteristic P-plastids have been observed and have confirmed the importance of this plastid as a systematic character of Caryophyllales.