Biao 810S is a chlorina mutant of the thermosensitive genic male sterile (TGMS) rice. We compared photosynthetic characteristics of these two lines. The contents of chlorophylls and carotenoids in Biao 810S were approximately half of those in 810S. However, the net photosynthetic rate (PN) of Biao 810S was higher than that of 810S under high irradiance or low concentration of carbon dioxide, and the photon quantum efficiency was higher than that of 810S. The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase in Biao 810S was only 69.80 % of that in 810S, but the activities of phosphoenolpyruvate carboxylase and NADP-malic enzyme were 79.50 and 69.06 % higher than those of 810S, respectively, suggesting that the efficiency of photon energy utilization in Biao 810S was enhanced by reduction of thermal dissipation and increase of electron transfer rate to generate sufficient assimilation power for the dark reactions. Consequently, the increased activities of C4 photosynthetic enzymes lead to more effective fixation of CO2 and the synergistic effect of light and dark reactions contributed to the higher PN of Biao 810S. and L.-J. Ou ... [et al.].
Photosynthetic characteristics were compared between plants of low altitude (LA) grown at LA (Palampur; 1 300 m) and at high altitude, HA (Kibber; 4 200 m), and plants naturally occurring at different altitudes (Palampur, 1 300 m; Palchan, 2 250 m; and Marhi, 3 250 m). Net photosynthetic rate (PN) was not significantly different between altitudes. However, the slopes of the curve relating PN to intercellular CO2 concentration (Ci) were higher in plants at Palchan, Marhi, and Kibber compared to those at Palampur, indicating that plants had higher efficiency of carbon uptake (the initial slope of PN/Ci curve is an indication) at HA. They had also higher stomatal conductance (gs), transpiration rate, and lower water use efficiency at HA. gs was insensitive to photosynthetic photon flux density (PPFD) for plants naturally occurring at Palampur, Palchan, and Marhi, whereas plants from LA grown at Palampur and Kibber responded linearly to increasing PPFD. Insensitivity of gs to PPFD could be one of the adaptive features allowing wider altitudinal distribution of the plants. and N. Kumar, S. Kumar, P.S. Ahuja.
High level of phosphoenolpyruvate carboxylase (PEPC) gene was stably inherited and transferred from the male parent, PEPC transgenic rice, into a female parent, japonica rice cv. 9516. Relative to the female parent, the produced JAAS45 pollen lines exhibited high PEPC activity (17-fold increase) and also higher photosynthetic rates (about 36 %-fold increase). The JAAS45 pollen lines were more tolerant to photoinhibition and to photo-oxidative stress. Furthermore, JAAS45 pollen lines, as well as their male parent, were tested to exhibit a limiting C4 cycle by feeding with exogenous C4 primary products such as oxaloacetate (OAA). Thus the PEPC gene and photosynthetic characteristics of PEPC transgenic rice could be stably transferred to the hybrid progenies, which might open a new breeding approach to the integration of conventional hybridization and biological technology. and L. Ling, B. J. Zhang, D. M. Jiao.
We investigated the effect of growth irradiance (I) on photon-saturated photosynthetic rate (Pmax), dark respiration rate (RD), carboxylation efficiency (CE), and leaf mass per unit area (LMA) in seedlings of the following four tropical tree species with contrasting shade-tolerance. Anthocephalus chinensis (Rubiaceae) and Linociera insignis (Oleaceae) are light-demanding, Barringtonia macrostachya (Lecythidaceae) and Calophyllum polyanthum (Clusiaceae) are shade-tolerant. Their seedlings were pot-planted under shading nets with 8, 25, and 50 % daylight for five months. With increase of I, all species displayed the trends of increases of LMA, photosynthetic saturation irradiance, and chlorophyll-based Pmax, and decreases of chlorophyll (Chl) content on both area and mass bases, and mass-based Pmax, RD, and CE. The area-based Pmax and CE increased with I for the light-demanders only. Three of the four species significantly increased Chl-based CE with I. This indicated the increase of nitrogen (N) allocation to carboxylation enzyme relative to Chl with I. Compared to the two shade-tolerants, under the same I, the two light-demanders had greater area- and Chl-based Pmax, photosynthetic saturation irradiance, lower Chl content per unit area, and greater plasticity in LMA and area- or Chl-based Pmax. Our results support the hypothesis that light-demanding species is more plastic in leaf morphology and physiology than shade-tolerant species, and acclimation to I of tropical seedlings is more associated with leaf morphological adjustment relative to physiology. Leaf nitrogen partitioning between photosynthetic enzymes and Chl also play a role in the acclimation to I. and Y.-L. Feng, K.-F. Cao, J.-L. Zhang.
Responses of photosynthetic gas exchange and chlorophyll (Chl) a fluorescence of three wild soybeans, Glycine soja, G. tomentella, and G. tabacina occurring in different habitats of Taiwan, to four NaCl treatments, 0S, LS, MS, and HS (i.e. 0, 17, 51, and 85 mM NaCl) were compared. In G. soja following exposure to NaCl treatment for one month, the photon saturated photosynthetic rate (PN), the ratio of variable to maximum fluorescence (Fv/Fm), the quantum yield of photosystem 2 (ΦPS2), and the electron transport rate (ETR) decreased dramatically. These reductions increased with increasing concentration of NaCl treatment. Plants of MS and HS treatments did not survive after extending the treatment to two months. Reductions in PN, ΦPS2, and ETR (but not in Fv/Fm) were found in G. tabacina after two months of exposure to MS and HS treatments, but the reduction was not as severe as that in G. soja. In G. tomentella, significant reductions in PN and gs were found only in HS plants after two months of treatment, but no significant differences in Fv/Fm, ΦPS2, and ETR were found among plants of the four treatments. Thus the three wild soybeans in Taiwan have differentiated in their photosynthetic susceptibility to salinity, G. tomentella being the least susceptible, G. soja the most sensitive, and G. tabacina the intermediate. Different mechanisms are attributed to the inhibition effect of salinity on photosynthesis of the three species. and W. Y. Kao, T. T. Tsai, C. N. Shih.
We compared the photosynthetic traits in response to soil water availability in an endangered plant species Mosla hangchowensis Matsuda and in a weed Mosla dianthera (Buch.-Ham.) Maxim. The highest diurnal mean net photosynthetic rate (PNmean), stomatal conductance (gs), and water use efficiency (WUE) of both species occurred at 60 % soil water holding capacity (WHC), while the lowest values occurred at 20 % WHC. The PNmean, gs, and chlorophyll (Chl) a and b contents of M. hangchowensis were lower than those of M. dianthera, while the physiological plasticity indices were higher than those of M. dianthera. M. hangchowensis had strong adaptability to the changing soil water status but weak extending population ability in its habitats because of the low PNmean, which may be one of the causes of its endangerment. and Y. Ge ... [et al.].
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.].
Thirty-day-old plants of mustard (Brassica juncea L.) were sprayed with 10-10, 10-8, or 10-6 M aqueous solution of 28-homobrassinolide (HBR). The HBR-treated plants were healthier than those treated with water and yielded more. Maximum increase over control was found in 60-d-old, 10-8 M-HBR-treated plants in fresh and dry mass per plant, carbonic anhydrase (CA, E.C. 4.2.1.1) activity, and net photosynthetic rate (PN), at harvest in number of pods per plant and seed yield per plant (the respective values were 25, 30, 34, 69, 24, and 29 %). A further increase in the concentration of HBR (10-6 M) did not make any additional impact on the growth and yield. Increased CA activity and PN were correlated with growth and seed yield. and S. Hayat ... [et al.].
4-year-old Pinus koraiensis, planted in open-top chambers at Changbai Mountain Station, received three different treatments [700 µmol(CO2) mol-1 = EC, control chamber = CC, and field = F]. Saturated net photosynthetic rate (PN) was 62 % higher in EC plants compared to CC and F plants as shown by PAR/PN response curves. Despite the increased PN, EC plants still showed decreased photosynthetic capacity when compared with CC and F plants at the same measurement CO2 concentration. EC plants had the highest stomatal conductance (gs) and ratio of intercellular to ambient CO2 concentration (Ci/Ca) compared with CC and F plants when measured at the same CO2 concentration. The Ci/Ca ratio was a sensitive indicator of stomatal behaviour, but not of photosynthesis. The responses of gs to EC did not correlate in magnitude or direction with responses of PN to EC. There was no significant difference in the number of stomata lines and stomata between EC and Ca. and Y. M. Zhou, S. J. Han.