Inhibition by Sethoxydim of Chloroplast Biogenesis, Development and Replication in Barley Seedlings

Abstract
Chloroplast Biogenesis, Inhibition of Chloroplast Replication, Sethoxydim. Sun-Type Chloroplast Sethoxydim not only blocks leaf growth and development of barley seedlings but also inhibits chloroplast biogenesis at all stages of development from proplastids to prochloroplasts, young and mature chloroplasts. Not only thylakoid synthesis, thylakoid multiplication and grana for­mation are affected, but also chloroplast replication. The chloroplasts of secondary leaves which before the sethoxydim application are in the stage of young, developing chloroplasts, remain in this differentiation stage when treated with sethoxydim. With their ultrastructural characteristics (e.g. lower stacking degree, higher proportion of exposed membranes, a lower thylakoid frequency etc.) they resemble sun-type chloroplasts. In the shoot meristem sethoxydim-treated plants contain only proplastids, whereas the plastids in the shoot meristem of control plants are already in the developmental stage between prochloroplasts to young chloroplasts. Mesophyll cells of sethoxydim-treated plants contain only one third of the chloroplasts found in the controls.

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