Recently, Werner and Stelzer reported C3 gas exchange simultaneous with CAM acid fluctuatíons, i.e., CAM-cycling, in seedlings of the mangrove species Rhizophora mangle L. The potential for CAM-cycling was investigated in mature individuals of R. mangle and of Laguncularia racemosa (L.) Gaertn. f in šitu in southwestem Florida and in seedlings of R. mangle grown in a growth chamber. Only C3 CO2 exchange was observed, while diumal fluctuatíons of tissue acid content were absent. Thus, no evidence for CAM-cycling was found in the field or in the growth chamber for R. mangle, nor in the field for L. racemosa.
Irrespective of the originál habitat of cassava {Manihot esculenta Crantz) cultivars, net photosynthetic rate (P^) was substantially reduced in leaves developed in a cool climate as compared with warm-climate leaves. Cool-climate leaves paitially recovered their photosynthetic capacity after 7 d acclimation in warm climate. The hot-climate cultivar showed a broad optimum temperature from 30 to 40 "C, while the cool-climate cultivar showed an upward shift in optimum temperature in the acclimated and warm-climate leaves. In field-grown cassava, maximum of upper canopy leaves was greater than 40 pmol(C02) m'^ s'i when measured in high rainfall season and the rates did not show saturation by radiant energy up to 1800 pmol m'2 s'i PAR. The seasonal average of upper canopy leaves was significantly correlated with both root yield and harvestable biomass. The selection for high in parental materials may lead to high yields when combined with other yield determinants.
Four dones of Miscanthus spp., collected from regions with different rainfall distribution, were transplanted in pots and subjected to five drying cycles (each of 6- 7 d). Gas exchanges were measured on attached leaves, The light-saturated photosynthetic CO2 uptake (P^) began to dechne when the leaf water potential (y\) was reduced to -1.3 - -1.5 MPa, and the values corresponding to 50 % decrease P^)] were -1.6 - -2.6 MPa. The P^ ) values were lower in a cloně collected from Kilung (northem Taiwan, highly frequent rainfall) than in dones collected from Kenting (southem Taiwan, distinct wet and dry season). Besides, the ^(1/2 Pj^) value became lower in all the tested dones when the drying cycle advanced (in the drying cycle of northem Taiwan cloně and in the 5‘*’ drying cycle of southem Taiwan dones, řespectively). Both the stomatal and non- stomatal factors of photosynthesis were affected by water deficit, and the osmotic adjustment mitigated the negative impact of water deficit on both factors. The clonal differences in the tolerance and acdimation of photosynthesis to water deficit are dosely related to the osmotic adjustment, and the clonal differences in osmotic adjustment reflect the rainfall pattem of sampled region.
Plants of Phaseolus vulgaris L. cv. Linden were grown at the current (35 Pa) oř the sub-ambient (20 Pa) partial pressures of CO2 at 29 ± 3 in order to analy2« the photosynthetic acclimatíon to low ambient CO2. No difference was observed in the CO2 response of net photosynthetic rate or leaf conductance (gi) below the CO2 partial pressure measurement of 35 Pa. Above 35 Pa, was depressed in plants grown at 20 Pa CO2 when compared to those grown at 35 Pa CO2. In both treatments, became insensitíve to increasing CO2 above an intercellular partial pressure of 50 Pa, indicating that the capacity of starch and sucrose synthesis to metabolize triose phosphates limited at hi^ measurement CO2. No differences were observed in the ribulose-l,5-bisphosphate carboxylase content, actívity, or actívation statě in plants grown at either CO2 partial pressure. Chlorophyll contents were also equivalent between the treatments. Hence, Uttle modulatíon of enzyme or pigment level follows atmospheric CO2 depletíon, with the possible exception that the capacity of starch and sucrose synthesis may be reduced in plants grown at low CO2.
Differences between photosynthetic characteristics of chlorophyll (Chl) 6-deficient aurea mutant (Su/su) and the green (su/su) variety of Nicotiana tabacum were tested. Fully mature leaves of 3-5-month-old plants grown in potted soil were investigated. Main differences were found as follows: Respective Chl a and b contents were 3 and 5 times lower in aurea plants, while xanthophylls and carotenes contents per unit of Chl were higher. The content of light-harvesting complex (LHC) was lower and LHC composition differed in aurea mutant. PS 1 activity calculated per unit of Chl content was higher in aurea mutant. The green variety showed the lower photosynthetic rates (Pn) at saturating irradiances whether calculated on the Chl or leaf area basis. At excessive light declined with green plants. Carboxylation efficiency (CE) (CO2 response slope of Pjj at low CO2 concentrations) was higher for aurea mutant. Time- integrated intercellular CO2 concentrations derived from ^^C discrimination were higher for aurea mutant (304 cm^ m'^) than for green plants (283 cm^ m'^), which together with higher mean stomatal conductance in aurea matched CE differences.
Depressions of the photosynthetic and respiration rates, found over a wide range of water stress, were remarkably reversible after resaturation of wheat leaf segments.
Sodium chloride (NaCl) concentratíons 200 to 900 mM enhanced the photosynthetic rate (Pn) both in whole leaves and in mechanically isolated, intact mesophyll cells of a salt marsh halophyte Sesuvium portulacastrum wilh a maximum at 600 mM NaCl. These changes were in agreement with changes in chlorophyll concentration in leaves. Though the increasing salt concentratíons resulted in leaf succulence, no change in the photosynthetic carbon pathway was observed.
Considerable increase in net photosynthetic rates ribulose-l-5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) activities, and pigment contents was observed in Helianthus annuus L. plants affected by different types of N-fertilization, but no cultivar variability was found. and water use efficiency (WUE) were enhanced strongly when the plants were treated with a combined compost (12N-12K-12P) or urea while manure induced a rather weak effect. The carboxylase activities changed wifli the N treatment and they were higly correlated with and WUE (r > 0.9). The RuBPC/PEPC ratios fell drastically in urea and 12N-12K-12P treated plants.
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.
Charactenstícs of the pigment apparatus were studied in plants grown from tubers of the oř 3’’^ doně generation of two cultivars of potato (Solanum tuberosum L) transformed with Agrobacterium tumefaciens strains. The cv. Zvíkov carries pRiA4b T-DNA of A. rhizogenes and the vector plasmid pGA472 T-DNA carrying the gene for kanamycin resistance. The cv. Kamýk carries the vector plasmid pCB1339 which contains the kanamycin resistance gene and the cytokinin synthesis gene. In the field experiments, the plant dry matter, the relative water content, the chlorophyll (Chl) a and b contents, the Chl a/b ratio and the course of slow Chl fluorescence induction curves were not signifícantly different in transformed and control plants. The amoímt of the Chl-protein complexes of the reaction centres of both photosystems separated by electrophoresis was similar for both transformed and control plants. Howevér, the content of oligomeric light-harvesting complex was significantly higher in both the transformants.