Various physiological characteristics of Cj and C4 plants (14 species) grown along a salinity gradient were studied. The majority of plants occupying salt-marshes were succulent chenopods, mainly C4 annuals. The ash content of assimilating organs of plants was higher and osmotic potential lower in species grown under increasing soil salinity. The plants of the NADP-ME group accumulated more K than Na. Large amounts of Na"^ and CT characterized the NAD-ME plants and perennial C3 plants from sites with high soil salinity, Net photosynthetic rate (P^) and chlorophyll content were decreased in species grown under high salinity. Dark respiration was depressed by salinity to a lesser extent than P^.
Changes in chlorophyll (Chl) a+b and a/b, senescence patterns during Chl loss and changes in net photosynthetic rate (P^) of four leaf flushes in Quercus acutissima and Q. serrata were studied. Emergent current-year leaves were classified according to the order of shoot growth flushes (first to fourth flush groups). Senescence patterns showed that leaf fall started from the leaf cohorts of the first flush group (the "oldest" leaf cohorts) which cuhninated upwards to the fourth leaf flush group (the "yoímgest" leaf cohorts). Senescence during Chl loss was accompanied by a decline in Pf^. A strong influence by the leaf flushing phenomenon on senescence was found which limited leaf bearing period and duration of Having large total leaf area and moderately long duration, tiie third and second leaf flush groups reflected the highest photosynthetic potential. This may be a positive attribute since the duration by which these plants maximize the use of its assimilatory organs is an important factor for their carbon fixation.
In the dimorphic stag’s hom fem, Platycerium coronarium (Koenig ex Mueller) Desv., photosynthetic characters and chlorophyll (Chl) contents were deteiinined in both nést and pendulous fronds at different stages of ontogeny and at different positions along the longest length of each frond. Area-specific radiant energy- saturated net photosynthetic (P^) and dark respiration rates, dry mass-specific Chl content and quantum yield increased during frond development and decreased when senescence set in. Radiant energy-saturated and dry-mass specific Chl content were greatest in the youngest tissues of each frond. In addition to the functions ascribed to the nést (water and nutrient collection) and pendulous (reproduction) fronds, the results indicate the important roles of both frond types in providing Chemical energy to the growth and survival of the plant.
Sodium chloride salinity had enhanced the photosynthetic rate, photosystem 2 activity and chlorophyll synthesis in isolated leaf cells of Ipomoea pescaprae up to 200 mM NaCl. The salt treated plants did not show any shift in the mode of photosynthesis.