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.
Morphological and ultrastructural changes, the chlorophyll (Chl) content and Chl a fluorescence induction were studied in primary leaves of runner beán plants (Phaseolus coccineus L. cv. Pi?kny Jaš) grown in Knop solution and treated with excess Cu [20 g(CuS04 x 5 H2O) m"^] at difíerent growth stages. The plants were exposed to the metal for 12 d. Cu added to the nutrient solution at the beginning growth stage induced significant leaf area reduction (31 %) as well as increase of Chl accumulation (148 %) and leaf density (122 %). No ultrastructural changes of chloroplasts were seen. Application of Cu at the advanced growth stage caused relatively smáli changes except local disturbances in stroma lamellae and leaf reduction to 70 % of control. Significant disorganization of chloroplast ultrastructure, smáli leaf area reduction (80 %) but specific leaf area increase (163 %) and leaf density decrease (67 %) were seen only in the primary leaves of plants treated with Cu at the finál stage of growth. These changes, similar to senescence response, were accompanied by Fy/Fo ratio decrease to 67 % in comparison with control.
During the growth cycle of micropropagated Juglans regia plantlets, phosphoenolpyruvate carboxylase (PEPC) activity was aiways higher than initial ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity. The ratio of PEPC/RuBPCO activities was higher during the first part of the exponential phase of growth and lower during the second part. The variations of PEPC activity were parallel to the soluble protein content and the variations of initial and total RuBPCO activities were parallel to the chlorophyll accumulation.
The ribulose 1,5-bisphosphate carboxylase (RuBPC) activity, protein content and net photosynthetic rate (P^) were estimated at monthly intervals from September 1990 to August 1991 in Chukrasia íabularis, Dolichandrom atrovirens, Eugenia jambolana, Gmelina arborea, Lamea coromandelica, Terminalia arjuna and Terminalia bellehca. The leaves of all these tree species showed significantly higher RuBPC activity during summer than in winter, when it was expressed on the basis of chlorophyll (Chl) content. RuBPC exhibited seasonal variations in its activity and these differed from one tree species to the other. When expressed on the basis of leaf area, the activity of RuBPC correlated with protein content, but not with P^.
The steady-state photosynthetic irradiance and temperature responses of Viola hondoensis and V. keiskei (Violaceae) growing in proximity in their nati ve environment and under three levels of artificial shade of relative irradiance (RI) of 7, 20 and 50 % were investigated. The maximum photosynthetic rates and temperature optima under natural conditions were much higher in V. keiskei than in V. hondoensis, except when in leaves of V. keiskei chlorophyll was degraded due to autumn frosts. When grown under artificial shade, both species had higher temperature optima as RI decreased. Since leaves under the three RI conditions experienced a similar leaf temperature, it was concluded that the shifts in the temperature responses with RI resulted from acclimation to the varying irradiance. The higher temperature optima observed in V. keiskei under natural conditions were probably due to the fact that V. keiskei grew in more shady microhabitats than V. hondoensis.