Photosynthetic pathways (C4, C3, and CAM species) and plant life forms of three grassland types in North China were compared. Of the total 201 species, 144 species in 78 genera and 34 families had C3 photosynthetic pathway, 56 species in 35 genera and 11 families had C4 photosynthetic pathway, and 1 species had CAM photosynthetic pathway. The number of C4 species in Songnen meadow was 70-80 % greater than that in Xilinguole steppe and Hunshandak desert grassland, but that for C3 species did not differ significantly among the three grassland types. The number of therophytes in the Songnen meadow was relatively greater than that of the other two grassland types, but that of hemicryptophytes was lower. Thus the distribution of C4 species and plant life form is probably related to precipitation.
Floristic compositions, life forms, reproductive types for forage species, and their responses to desertification in Hunshandake desert were studied. 164 species, in 30 families and 94 genera, were identified with C3 (137 species), C4 (25 species), and CAM (2 species) photosynthesis. Of the 25 C4 species, 76 % were grasses and Chenopodiaceae species (hereafter chenopods). This suggests that the C4 species mainly occurred in a few families in the desert region. The reduction of C3 species and the increase of C4 species with desertification indicated that C4 species might have higher tolerance to environmental stresses (e.g. dry and poor soil). Relatively more hemicrytophyte and therophyte forms in the desert are related to the local temperate climate and vegetation dynamics. Relatively greater proportions of C4/C3 and clonal species/sexual species at mobile dune showed that the C4 species and clonal species could make greater contribution to sand land restoration in the Hunshandake desert.
The olive tree (Olea europaea L.) is commonly grown in the Mediterranean area, where it is adapted to resist periods characterized by severe drought and high irradiance levels. Photosynthetic efficiency (in terms of Fv/Fm and ΦPSII), photochemical (qP) and nonphotochemical quenching (NPQ) were determined in two-year-old olive plants (cultivars Coratina and Biancolilla) grown under two different light levels (exposed plants, EP, and shaded plants, SP) during a 21-day controlled water deficit. After reaching the maximum level of drought stress, plants were rewatered for 23 days. During the experimental period, measurements of gas exchange and chlorophyll (Chl) fluorescence were carried out to study the photosynthetic performance of olive plants. The synergical effect of drought stress and high irradiance levels caused a reduction of gas exchange and photosynthetic efficiency and these decreases were more marked in EP. EP showed a higher degree of photoinhibition, a higher NPQ and a lower qP if compared to SP. Coratina was more sensitive to high light and drought stress but also showed a slower recovery during rewatering, whereas Biancolilla showed a less marked photosynthesis depression during drought and a considerable resilience during rewatering. The results confirm that photoinhibition due to high light intensity and water deficit can be an important factor that affects photosynthetic productivity in this species. and A. Sofo ... [et al.].
Morphological, anatomical and physiological frond traits of Cheilanthes persica (Bory) Mett. ex Kuhn were studied to analyze its adaptive strategy. Mean frond life span is about 340 d. Mature fronds are characterized by 91 g m-2 areal dry mass (ADM) and 217 g m-2 succulence. The reduction of frond water content in July (dehydration phase) caused a 51 % decrease in frond surface area (SA). Fronds were dry in August (desiccation phase); nevertheless, in September they showed an increased SA (rehydration phase). Chlorophyll (Chl) a/b ratio, above 3, and the well developed palisade parenchyma (two layers, total thickness of 103.9 µm) are typical for sun leaves. Chl and carotenoid contents and net photosynthetic rate (PN) increased during frond development until the highest values in April-May (maturity phase). When mean air temperature reached 31.3 °C, stomatal conductance (gs) decreased by 34 % and PN by 33 %. The high pigment contents can dissipate the excess of radiant energy, particularly under unfavourable conditions, when PN is low. Rather high PN was found during the rehydration stage. The pronounced decline of mesophyll activity during the declining phase was confirmed by the lowest PN. and L. Gratani, M. F. Crescente, G. Rossi.
In vivo chlorophyll fluorescence analysis reflecting the photosystem II functionality was investigated in the cyanobacterium Anabaena variabilis PCC 7937 under simulated solar radiation in a combination with various cut-off filters (WG 280, WG 295, WG 305, WG 320, WG 335, WG 345, and GG 400) to assess the effects of photosynthetically active radiation (PAR), ultraviolet-A (UV-A), and ultraviolet-B (UV-B) radiations on photosynthesis. The photosynthetic activity (PA) was severely inhibited immediately after 10 min of exposure to high PAR, UV-A, and UV-B radiations compared with low PAR grown control samples. After 1 h of exposure, PA of 17.5 ± 2.9% was detected in the high PAR exposed samples compared with the control, while only a trace or no PA was observed in the presence of ultraviolet radiation (UVR). A recovery of PA was recorded after 2 h of the exposure, which continued for next 4, 8, 12, and 24 h. After 24 h of the exposure, PA of 57.5 ± 1.9%, 36.1 ± 11.7%, 23.5 ± 3.3%, 22.3 ± 5.2%, 20.8 ± 6.7%, 13.2 ± 6.6%, and 21.6 ± 9.5% was observed compared with the control sample in 400, 345, 335, 320, 305, 295, and 280 nm cut-off filters-covered samples, respectively. The relative electron transport rate, measured after 24 h exposure, showed also a disturbance in electron transfer between the two photosystems under the high PAR and UVR treatments relative to the control samples, suggesting the inhibition of photosynthesis. This study suggests that both high PAR and UVR inhibited the photosynthetic performance of A. variabilis PCC 7937 by damaging the photosynthetic apparatus, however, photoprotective mechanisms evolved by the organism allowed an immediate repair of ecologically important machinery, and enabled its survival., S. P. Singh ... [et al.]., and Obsahuje bibliografii
Diurnal variation in net photosynthetic rate (PN) of three-year-old plants of Ginkgo biloba was studied under open, O (receiving full sunlight), net-shade, NS (40 % of photosynthetically active radiation, PAR), or greenhouse, G (25 % PAR) conditions. In all three conditions, PN was higher in morning along with stomatal conductance (gs), and intercellular CO2 concentration (Ci), while leaf temperature and vapour pressure deficit were low. The O-plants exhibited a typical decline in PN during midday, which was not observed in NS-plants. This indicated a possible photoinhibition in O-plants as the ratio of variable to maximum fluorescence (Fv/Fm) and photosystem 2 (PS2) yield (ΦPS2) values were higher in the NS- and G-plants. On the contrary, stomatal density and index, chlorophyll a/b ratio, leaf thickness, and density of mesophyll cells were greater in O-plants. Further, higher PN throughout the day along with higher relative growth rate under NS as compared to O and G suggested the better efficiency of Ginkgo plants under NS conditions. Therefore, this plant species could be grown at 40 % irradiance to meet the ever-increasing demand of leaf and also to increase its export potential. and S. Pandey, S. Kumar, P. K. Nagar.
The effects of shade on the growth, leaf photosynthetic characteristics, and chlorophyll (Chl) fluorescence parameters of Lycoris radiata var. radiata were determined under differing irradiances (15, 65, and 100% of full irradiance) within pots. The HI plants exhibited a typical decline in net photosynthetic rate (PN) during midday, which was not observed in MI- and LI plants. This indicated a possible photoinhibition in HI plants as the ratio of variable to maximum fluorescence (Fv/Fm) value was higher and the minimal fluorescence (F0) was lower in the, and LI plants. Diurnal patterns of stomatal conductance (gs) and transpiration rate (E) were remarkably similar to those of PN at each shade treatments, and the intercellular CO2 concentration (Ci) had the opposite change trend. Under both shading conditions, the light saturation point, light compensation point and photon-saturated photosynthetic rate (Pmax) became lower than those under full sunlight, and it was the opposite for the apparent quantum yield (AQY). The higher the level of shade, the lower the integrated daytime carbon gain, stomatal and epidermis cell densities, specific leaf mass (SLM), bulb mass ratio (BMR), leaf thickness, and Chl a/b ratio. In contrast, contents of Chls per dry mass (DM), leaf area ratio (LAR), leaf mass ratio (LMR), leaf length, leaf area and total leaf area per plant increased under the same shade levels to promote photon absorption and to compensate for the lower radiant energy. Therefore, when the integrated daytime carbon gain, leaf area and total leaf area per plant, which are the main factors determining the productivity of L. radiata var. radiata plant, were taken into account together, this species may be cultivated at about 60-70% of ambient irradiance to promote its growth. and S. B. Zhou ... [[et al.].
The photosynthetic performances of regenerated protoplasts of Bryopsis hypnoides, which were incubated in seawater for 1, 6, 12, and 24 h, were studied using chlorophyll (Chl) fluorescence and oxygen measurements. Results showed that for the regenerated protoplasts, the pigment content, the ratios of photosynthetic rate to respiration rate, the maximal photosystem II (PSII) quantum yield (Fv/Fm), and the effective PSII quantum yield (ΦPSII) decreased gradually along with the regeneration progress, indicated that during 24 h of regeneration there was a remarkable reduction in PSII activity of those newly formed protoplasts. We assumed that during the cultivation progress the regenerated protoplasts had different photosynthetic vigor, with only some of them able to germinate and develop into mature thalli. The above results only reflected the photosynthetic features of the regenerated protoplasts at each time point as a whole, rather than the actual photosynthetic activity of individual aggregations. Further investigation suggested a relationship between the size of regenerated protoplasts and their viability. The results showed that the middle-sized group (diameter 20-60 μm) retained the largest number of protoplasts for 24 h of growth. The changes in Fv/Fm and ΦPSII of the four groups of differently sized protoplasts (i.e. < 20, 20-60, 60-100, and > 100 μm) revealed that the protoplasts 20-60 μm in diameter had the highest potential activity of the photosynthetic light energy absorption and conversion for several hours. and F. Lü, G. C. Wang, J. F. Niu.
Photosynthetic irradiance response of vegetative and reproductive structures of the green-flowered deciduous perennial green hellebore was studied by the comparative use of chlorophyll (Chl) fluorescence techniques and gas exchange measurements. All the Chl-containing organs (leaves, sepals, stalks, and fruits) examined were photosynthetically active showing high intrinsic efficiencies of photosystem 2 (Fv/Fm: 0.75-0.79) after dark adaptation. Even in the smaller fertile and sterile parts of the flower (nectaries and anthers) a remarkable photosynthetic competence was detected. With increasing photon flux densities (PFD) electron transport rates, actual quantum yields, and photochemical quenching coefficients of the main photosynthetic organs decreased in the order: leaf>sepal>fruit>stalk. At moderate to high PFDs the sepals achieved maximum electron transport rates corresponding to about 80 % of concomitant mature leaves. In contrast, maximum net photosynthetic rate of the sepals [2.3 μmol(CO2) m-2 s-1] were less than one fourth of the leaves [10.6 μmol(CO2) m-2 s-1]. This difference is explained by a 70-80 % lower stomatal density of sepals in comparison to leaves. As the basal leaves emerge late during fruit development, the photosynthetically active sepals are a major source of assimilates, contributing more than 60 % of whole-plant CO2 gain in early spring. The ripening dehiscent fruits are characterized by an effective internal re-fixation of the respirational carbon loss and thus additionally improve the overall carbon budget. and G. Aschan ... [et al.].
Photosynthesis and leaf traits of five species in genus Cypripedium were compared in natural habitats and transplant nursery to develop effective strategy for cultivation and conservation. Among five species, C. guttatum had the highest photosynthetic capacity
(PNmax) in the natural habitat and nursery, while C. lichiangense the lowest. The differences in PNmax among species were correlated with leaf N content (LNC) and leaf dry mass per unit area (LMA). After transplanting from natural habitats to nursery, the
PNmax of C. lichiangense and C. yunnanense decreased, that of C. guttatum increased, while those of C. flavum and C. tibeticum remained relatively constant. The variations in LNC and biochemical efficiency would be responsible for the differences in
PNmax between plants in natural habitats and in the nursery, but not the relative stomatal limitation. After transplanting, the Fv/Fm of C. lichiangense and C. yunnanense were declined. Meanwhile, the temperature ranges maintaining 90 % PNmax of C. lichiangense and C. yunnanense were narrower than those of the other three species. Thus the biochemical process in five species played a major role in the differences of PNmax after transplanting, and the widespread species had higher photosynthetic adaptability than the narrow-spread species. and S.-B. Zhang ... [et al.].