Net photosynthetic rate growth and flower and firoit settíng pattems were studied in two cultivars of bell-pepper (Ccpsicum annuum L. cv. Arka Mohini, a detenninate type and Arka Basant, an indetenninate type) grown at two different night temperatures. and growdi were higher at high night temperature (27/22 <*C, day/night) dian at low night temperature (27/17 °C) in bodl cultivars. The flower and fitiit numbers were higher in die plants grown at 27/17 °C than at 27/22 oC.
The effect of defolíation on net photosynthetic rate (Pn), dry matter production and fruit growth was studied in bell-pepper (Capsicum annuum L. cv. Arka Gaurav). Considerable differences in were observed between defoliated and non-defoliated plants. Defolíation influenced the total dry matter production, leaf area and the relative growth rate of the plants. The bell-pepper has the capacity to compensate photosynthetically for a certain degree of defolíation without reducing the biological yield. No significant differences in the dry matter of fruits per plant were foímd between defoliated and non-defoliated plants.
The kinetics of Ig-positive cell populations in carp tissues was followed during an infection with the gut dwelling coc-cidian Goussia carpelli Léger et Stankovich, 1921. In cell suspensions of the anterior and posterior sections of the intestine, the proportion of Ig-positive cells increased with the development of the coccidia and peaked during oocyst formation at day 15 post exposure. These results suggest a reaction of the local mucosal immune system. In cell suspensions of pronephros the proportion of Ig-positive cells increased as well, indicating that a systemic immune response was also induced against this intestinal cocci-dian parasite of carp.
In tomato {Lycopersicon esculentum L.) plants, net carbon dioxide exchange rate (P]si) response curves to both irradiance (/) and short-term [CO2] were similar for plants grown at both 350 and 700 cm3(C02) m'^. However, water vapor conductance (gHjo) of plants grown at high [CO2] was less sensitive to short term [CO2] variations, when measured at low vapor pressure difference, and was larger than the conductance of "ambient [CO2]" plants when both were exposed to high [CO2]. Pn and gHjO under high I increased with temperature over the range 18 to 32 °C. of plants grown in both [CO2] treatments increased at most about 25 % from 350 to 700 cm3 m-3 at 18 and 25 °C, and decreased when exposed to 1000 cm^ m'^ at these temperatures. Thus increasing atmospheric [CO2] might not increase P^ by as much as expected and water use of crops might not decrease.
Young (12 years old) Norway spruce {Picea abies [L.] Karst.) trees were exposed to ambient CO2 or ambient + 350 |niiol(C02) moL' continuously over 2 growing seasons in open-top chambers, under field conditions of a mountain stand. Comprehesive analysis of CO2 assimílation was performed after 4 and 22 weeks of the second growing season to evaluate the influence of elevated atmospheric CO2. A combination of gas exchange and a mathematical model of ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity was ušed. After 4 weeks of exposure no statistically significant stimulation of the radiant energy and CO2 saturated rate of CO2 uptake (ENsat) by the elevated CO2 concentration was found. Yet after 24 weeks a statistically significant depression of Ejvjsa, (38 %) and carboxylation efficiency (32 %) was observed. Depression of photosynthetic activity by elevated CO2 resulted from a decrease in the RuBPCO carboxylation rate. The electron transport rate was also modified similarly to the rate of RuBP formation. An accompanying decrease in nitrogen content of the needles (by 12 %) together with an increase in total saccharides (by 34 %) was observed after 24 weeks of exposure to enhanced CO2.
In a chlorophyll(Chl)-deficient ch5 mutant of Arabidopsis thaliana the thylakoid membrane of which is more loosely arranged than that of the wild type we characterized the xanthophyll cycle (VAZ cycle) components (violaxanthin - V, antheraxanthin - A and zeaxanthin - Z) in comparison with the wild type grown under three low irradiances. As the irradiance increased from 30 to 250 pmol m'^ s'i, the total amount of components of the VAZ cycle decreased in both biotypes, but those of the ch5 mutant decreased more slowly than did those of the wild type. In both biotypes, the relative amoímts of V and A decreased as the irradiance increased, and that of Z increased, but the increase and decrease in the ch5 mutant was slower than in the wild type. The epoxidation index showed that the VAZ cycle operated at a similar efficiency in both biotypes (between 30 and 250 pmol m‘2 s'*), but that the ch5 mutant worked at a capacity 3.5-13.5 % lower than did the wild type, depending on the irradiance. Thus in Chl-deficient mutants, the VAZ cycle operates at a lower capacity than in the wild type, and the mutants are more sensitive to the changes in irradiance.
Leaf adaptatíons of Quercus ilex L., Phillyrea latifolia L. and Pistacia lentiscus L. to various environmental conditions námely from the viewpoint of the differences of leaf area, dry mass, chlorophyll (Chl) content, sclerophylly index, succulence index and net photosynthetic rate are shown. Irradiance was the most important factor to miluence leaf temperature, stomatal conductance (g^) and transpiration rate (E). Under canopy layer low red-far red ratio reduced Pn- Shade leaves were enriched by Chl b. Chl content and sclerophylly index were good leaf characteristics to express adaptability of plants to microclimate.
Leaf conductance (g), net photosynthetic carbon fixation rate (Pyi), leaf protein concentration and ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity were examined in baldcypress {Taxodium distichum L.) seedlings subjected to rhizosphere hypoxia. Seedlings grown in nutrient solution were treated with either air or N2. Changes in g. Pyj, leaf protein concentrations and RuBPCO activity in response to the treatments were measured at 12, 24, and 48 h. In a second experiment, similar measurements were conducted on plants grown in soil medium under either flooded or drained conditions over a period of 28 d. Under rhizosphere hypoxia, both g and Pyj were reduced significantly at 24 and 48 h as compared to control plants while there were no significant differences in leaf protein concentrations between treatments. RuBPCO activity, however, was reduced significantly (27 % reduction) at 48 h. In flooding experiment, g and decreased on days 3, 5, and 10 significantly. RuBPCO activity was significantly lower in flooded plants as compared to control (aerated) plants on day 3 and 5 following initiation of flooding. bi this experiment, g and began to improve after day 10, to as much as 97 and 87 % of control by day 28, respectively. RuBPCO activity which had decreased significantly by day 3, remained significantly lower on day 5 and slightly (but not significantly) lower than in control plants during the remainder of the experiment. Present data support the hypothesis that in baldcypress seedlings, reduced RuBPCO activity is among the early signals of flood-stress contributing to the loss of leaf Pyj. In addition, plant acclimated to the stress conditions during the long-term experiment indicating that some flood-tolerant tree species such as baldcypress may occupy wet sites due to such capabilities.
The effect of heat stress (35 to 50 °C) on photosynthesis was investigated in heat tolerant (N 22) and heat sensitive (IR 8) cultivars of rice {Oryza sativa L.). The net photosynthetic rate showed greater thermal stability in N 22 than in IR 8. The relative dechne of the rate of whole chain electron transport and photosystem 2 (PS2) activity was more pronounced in IR 8 than N 22. In both cultivars photosystem (PSI) activity was stimulated by thermal treatment. Chlorophyll (Chl) a fluorescence transient arising ffom PS2 showed inhibition in both cultivars at 45 and 50 °C. Maximum fluorescence decreased more in IR 8 than in N 22 by high temperature treatment.