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Rooted cuttings of grapevines (Vitis vinifera L. cv. Sultana; syn. Thompson Seedless) were grown under glasshouse conditions and supplied with dilute nutrient solution containing either 0 or 90 mM of added NaCl. Growth and photosynthetic response to salt treatment and subsequent recovery were followed over 80 days. Shoot growth and photosynthesis were reduced by salt treatment. At relatively low concentrations of leaf chloride (< c. 150 mM, on a tissue water basis), photosynthetic reduction was largely due to increased stomatal resistance. Internal disturbances were involved at higher leaf Cl- concentrations (> c. 150 mM) and included an apparent reduction in photochemical efficiency and a faster rate of photorespiration. Levels of fraction I protein, and specific activity of ribulose-1,5-bisphosphate carboxylase measured in vitro, were not reduced by salt treatment. Vines showed remarkable adaptation to salinity insofar as leaves maintained positive turgor despite leaf Cl- concentrations exceeding 300 mM, implying osmotic adjustment. Cessation of salt treatment led to an immediate decrease in leaf Cl-, a promotion of shoot growth and a progressive recovery in photosynthesis accompanied by a marked but not necessarily concurrent reduction in both stomatal and internal resistances. Leaves tolerated Cl- levels up to 200 mM (under glasshouse conditions) without sustaining permanent reduction in photosynthetic activity. New shoots formed subsequent to stress relief are not a prerequisite for Cl- retranslocation from mature leaves as decapitation at the time of stress relief did not prevent attenuation of leaf Cl- or recovery in photosynthesis.

The role of chloroplast (cp) DNA in plastid and chloroplast function is discussed, particularly in relation to the interaction with nuclear DNA. The evolution of the chloroplast genome and the endosymbiont hypothesis are related to our results and those of others which show the occurrence of cpDNA sequences common to the nuclear and chloroplast genome.

In a study of the development of the second leaf of seedling wheat, the contents per lamina of fraction 1 protein and total soluble protein increased for 6 days after leaf emergence, and the contents of cytoplasmic and chloroplast rRNA for 5 days. Net synthesis of fraction 1 protein per unit of cyto-plasmic and chloroplast rRNA decreased with time. During the growth phase, incorporation of radioactive amino acids into fraction 1 protein was proportional to the amount of, rather than the rate of increase of, fraction 1 protein. After the maximum content of fraction 1 protein had been reached, incorporation into fraction 1 protein decreased both with time and relatively to other soluble proteins. The content of RNA and the proportion of rRNA found in cytoplasmic and chloroplast polyribosomes also fell. The rate of decrease in incorporation into fraction 1 protein exceeded the rate of decrease in chloroplast polyribosomes. We conclude that chloroplast polyribosomes are active in the turnover of fraction 1 protein large subunit during the growth phase, but are proportionately more active in making other proteins in older leaves.