The relationship between light-saturated photosynthetic capacity
(Pmax) and leaf nitrogen (N) content was investigated for one year in a 15-year-old Chamaecyparis obtusa canopy and was compared with a Cryptomeria japonica canopy previously described. The linear regression between P max and leaf N content tended to converge toward a single line segment from July to January and in May for C. obtusa. The slope of the linear regression between Pmax and leaf N content of C. obtusa was gentler than that of C. japonica. The smaller regression coefficient of C. obtusa may reflect species differences in nitrogen nutrition requirements between C. obtusa and C. japonica. A pronounced decrease in the slope of the linear regression lines due to low temperature was observed in February and March. During this period, P max of C. obtusa declined more than that of C. japonica suggesting that C. obtusa is less tolerant to low temperatures than C. japonica., H. Kobayashi, S. Inoue, and K. Gyokusen., and Obsahuje bibliografii
Syntrichia caninervis Mitt. is the dominant species in the moss crusts of the Gurbantunggut Desert, Northwestern China. We experimented with this species under controlled environmental conditions. Modulated chlorophyll (Chl) fluorescence was used to test the speed of recovery as evidenced by the time course of photosynthetic activity following remoistening. Transmission electron microscopy was used to explore the cytological characteristics of the leaf cells. Minimum and maximum fluorescence (F0 and FM) and photosynthetic yield (FV/FM) of photosystem II (PSII) recovered quickly when shoots were remoistened in the dark. This was especially the case of FV/FM; within the first minute of remoistening this reached 90% or more of the value attained after 30 min. These physiological changes were closely paralleled by cytological changes that indicated no damage to membranes or organelles. Correlation analysis showed that Chl fluorescence decreased both above and below a narrow moisture optimum. Our results underline the capability of S. caninervis to photosynthesize after remoistening. Utilizing precipitation events such as dew, fog, rain, and melting snow allows S. caninervis to survive and grow in a harsh desert environment. and J. Zhang ... [et al.].
Water and nitrogen (N) deficiency are two major constraints limiting the yield and quality of many oilseed crops worldwide. This study was designed to assess the response of Camelina sativa (L.) Crantz to the availability of N and water resources on photosynthesis and yield parameters. All the measured variables, which included plant height, root and shoot dry matter, root:shoot ratio, xylem pressure potential (XPP), yield components, photosynthetic parameters, and instantaneous water-use efficiency (WUE) were remarkably influenced by water and nitrogen supply. Net photosynthetic rate (PN) and yield components were significantly decreased more by water deficit than by N deficiency. XPP, stomatal conductance (gs), and intercellular CO2 concentration (C i) decreased substantially as the water deficit increased irrespective of the level of N application. WUE at the high N supply [100 and 150 kg(N) ha-1] dropped in a large degree as the increased water deficit due to a larger decrease in PN than transpiration rate (E). The results of this study suggest that the regulative capacity of N supply on photosynthetic and plant growth response is significantly affected by soil water status and C. sativa is more sensitive to water deficit than N supply. and X. Pan ... [et al.].
The study was carried out in a four-year-old super-high density olive grove in Central Italy to compare leaf gas exchanges of Spanish Arbequina and Italian Maurino olive cultivars. Overall, from mid July to mid November, Maurino had a slightly higher maximum
light-saturated net photosynthetic rate (PNmax) than Arbequina. The lowest and the highest PNmax values were recorded at the end of July and in mid November, respectively. Current-season leaves showed similar or slightly higher PNmax values than one-year-old leaves. During the day Maurino always had slightly higher values or values similar to Arbequina, with the highest PNmax being in the morning. Maurino had similar or higher dark respiration rate (RD) values compared to Arbequina. During the day, in both cultivars the RD was lower at 9:00 than in the afternoon. The pattern of the photosynthetic irradiance-response curve was similar in the two genotypes, but the apparent quantum yield (YQ) was higher in Maurino. In both cultivars intercellular CO2 concentration (Ci) tended to increase when PNmax decreased. The increase in Ci corresponded to a decrease in stomatal conductance (gs). The transpiration rate (E) increased from mid July to the beginning of August, then decreased in September and increased again in November. Particularly in the morning, the current-season leaves showed similar or slightly higher E values than the one-year-old leaves. During the day, in both cultivars and at both leaf ages, E was higher in the afternoon. No effects on leaf gas exchanges due to the presence or absence of fruit on the shoot were found. Overall, there was satisfactory physiological adaptation for Arbequina to the conditions of Central Italy and for Maurino to the superintensive grove conditions., P. Proietti, L. Nasini, and L. Ilarioni., and Obsahuje bibliografii
In order to investigate the effect of chromosome doubling on ozone tolerance, we compared the physiological responses of a diploid honeysuckle (Lonicera japonica Thunb.) and its autotetraploid cultivar to elevated ozone (O3) exposure (70 ng g-1, 7 h d-1 for 31 d). Net photosynthetic rate (PN) of both cultivars were drastically (P<0.01) impaired by O3. Although there were significantly positive correlation between PN and stomatal conductance (gs) in both cultivars under each treatment, the decreased gs in O3 might be the result rather than the cause of decreased P N as indicated by stable or increasing the ratio of intercellular to ambient CO2 concentration(Ci/Ca). PN under saturating CO2 concentration
(PNsat) and carboxylation efficiency (CE) significantly decreased under O3 fumigation, which indicated the Calvin cycle was impaired. O3 also inhibited the maximum efficiency of photosystem II (PSII) photochemistry in the dark-adapted state (Fv/Fm), actual quantum yield of PSII photochemistry (ΦPSII), electron transport rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching (NPQ), the maximum in vivo rate of Rubisco carboxylation (Vcmax) and the maximal photosynthetic electron transport rate (Jmax) which demonstrated that the decrease in PN of the honeysuckle exposed to elevated O3 was probably not only due to impairment of Calvin cycle but also with respect to the light-harvesting and electron transport processes. Compared to the diploid, the tetraploid had higher relative loss in transpiration rate (E), (gs), (PNsat), Vcmax and Jmax. This result indicated that the Calvin cycle and electron transport in tetraploid was damaged more seriously than in diploid. A barely nonsignificant (P=0.086) interaction between O3 and cultivar on PN suggested a higher photosynthetic sensitivity of the tetraploid cultivar. and L. Zhang ... [et al.].
Responses of leaf gas exchange, fluorescence emission, chlorophyll concentration, and morpho-anatomical features to changes in photosynthetic photon flux density (PPFD) were studied in three wild ornamental species of Passiflora L. to select sun and shade species for landscaping projects. Artificial shade was obtained with different shading nylon nets, under field conditions, which allowed the reduction of 25, 50, and 75% of global radiation, along with a control treatment under full sunlight. For Passiflora morifolia the highest mean values of light-saturated net photosynthetic rate (PNmax) and light compensation point (LCP) were observed at 50 and 25% shade, respectively, while the highest values of dark respiration rate (RD) and apparent quantum yield (α) were observed at 75% shade. For Passiflora suberosa litoralis the highest value of P max was observed at full sunlight. The highest mean values for Pmax, RD, and LCP for Passiflora palmeri var. sublanceolata were obtained at 25% shade. The highest values of net photosynthetic rate (PN) for P. morifolia, P. palmeri var. sublanceolata, and P. suberosa litoralis were 21.09, 16.15, and 12.36 μmol(CO2) m-2 s-1, observed at 50 and 75% shade and full sunlight, respectively. The values of the minimal chlorophyll fluorescence (F0) were significantly different in P. suberosa litoralis and P. palmeri var. sublanceolata, increasing with the increase of the irradiance. In contrast, the values of maximum photochemical efficiency of PSII (Fv/Fm) were significantly different only in P. suberosa litoralis, being higher at 75%, progressively reducing with the increase of PPFD levels. The total concentration of chlorophyll (Chl) was higher in shaded plants than in the ones cultivated in full sunlight. On the other hand, the values of Chl a/b ratio were reduced in shaded plants. A significant effect of shade levels on leaf area (LA) and specific leaf area (SLA) was found for the three species, whose highest mean values were observed at 75% shade. The thickness of foliar tissues was significantly higher for the three species at full sunlight and 25% shade. These results suggested that P. morifolia and P. palmeri var. sublanceolata appeared to be adapted to moderate shade conditions. P. suberosa litoralis presented higher plasticity to greater variation of the irradiance levels, while the photoinhibition was one of the limiting factors for this species at full sunlight. and M. V. Pires ... [et al.]
An early senescence (es) mutant of rice Oryza sativa L. with progressing death of most of leaves before heading stage was identified in the field in Hainan province. After tillering stage, the brown striations were found in the base of green leaves randomly, and then expanded to whole leaves. No fungi, bacteria, and viruses were detected in the brown striations suggesting that it was a genetic mutant. The ultrastructure of leaf cells at the site of brown striations showed breakdown of chloroplast thylakoid membrane structures and other organelles, and condensation of the cytoplasm at severe senescence stage. The photosynthetic activity and chlorophyll (Chl) contents decreased irreversibly along with leaf senescence process. and L. F. Wang, Y. Y. Chen.
Australian carnivorous pitcher plant Cephalotus follicularis Labill. produces two types of leaves. During the spring time, the plant produces a foliage type of noncarnivorous leaf called lamina. Later, the second type of leaf is produced - carnivorous pitcher. Using simultaneous measurements of gas exchange and chlorophyll (Chl) fluorescence photosynthetic efficiency of these two distinct forms of leaves were compared. In addition stomatal density, an important component of gas exchange, and Chl concentration were also determined. Pitcher trap had lower net photosynthetic rate
(PN) in comparison to noncarnivorous lamina, whereas the rate of respiration (RD) was not significantly different. This was in accordance with lower stomatal density and Chl concentration in the pitcher trap. On the other hand maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of photochemical energy conversion in PSII (ΦPSII) was not significantly different. Nonphotochemical quenching (NPQ) was significantly higher in the lamina at higher irradiance. These data are in accordance with hypothesis that changing the leaf shape in carnivorous plants to make it a better trap generally makes it less efficient at photosynthesis. However, the pitcher of Cephalotus had much higher PN than it was expected from the data set of the genus Nepenthes. Because it is not possible to optimize for contrasting function such as photosynthesis and carnivory, it is hypothesized that Cephalotus pitchers are less elaborated for carnivorous function than the pitchers of Nepenthes. and A. Pavlovič.
Photosynthetic properties of carnivorous plants have not been well characterized and the extent to which photosynthesis contributes to carbon gain in most carnivorous plants is also largely unknown. We investigated the photosynthetic light response in three carnivorous plant species, Drosera rotundifolia L. (sundew; circumpolar and native to northern British Columbia, Canada), Sarracenia leucophylla Rafin. ('pitcher-plant'; S.E. United States), and D. capensis L. (sundew; Cape Peninsula, South Africa), using portable gas-exchange systems to explore the capacity for photosynthetic carbon gain in carnivorous plant species. Maximal photosynthetic rates (1.32-2.22 μmol m-2 s-1 on a leaf area basis) and saturating light intensities (100 to 200 μmol PAR m-2 s-1) were both low in all species and comparable to shade plants. Field or greenhouse-grown D. rotundifolia had the highest rates of photosynthesis among the three species examined. Dark respiration, ranging from -1.44 (S. leucophylla) to -3.32
(D. rotundifolia) μmol m-2 s-1 was high in comparison to photosynthesis in the species examined. Across greenhouse-grown plants, photosynthetic light compensation points scaled with light-saturated photosynthetic rates. An analysis of gas-exchange and growth data for greenhouse-grown D. capensis plants suggests that photosynthesis can account for all plant carbon gain in this species. and B. M. Bruzzese ... [et al.].
We compared light-saturated photosynthetic rates and their stomatal limitations among Cryptomeria japonica trees with a similar height but different current growth rates. Although
slow-growing trees had a lower stomatal conductance and a higher carbon isotope ratio in shoots, the stomatal limitations in photosynthesis were not different. Large mesophyll CO2 diffusion resistance contributed to the low photosynthetic rate of the
slow-growing trees., T. Tange ... [et al.]., and Obsahuje bibliografii