Changes in photosynthetic attributes related to genetic improvement of cotton yield were studied in seven Chinese cotton cultivars widely grown in Xinjiang during the past 30 years. Our results showed that a chlorophyll (Chl) content and net photosynthetic rate (PN) of the 1980s cultivar was the highest among all after 60 days from planting (DAP). However, after 75 DAP, the Chl content, PN, and actual photochemical efficiency of PSII of the old cultivars declined gradually, whereas those of the new cultivars remained relatively high. Compared to the old cultivars, leaves of the new cultivars endured a longer period and their senescence was slower, shoot and boll dry mass was higher, but the root to shoot ratio was lower. The lint yield of the 2000s cultivars was 14.7 and 21.4% higher than that of 1990s and 1980s cultivars, respectively. The high yield of the new cultivars was attributed to a greater number of bolls per unit of area with high lint percentage. We suggested that the improved photosynthetic capacity and the increased ability to deliver photosynthates to reproductive sites during the peak boll-setting stage to boll-opening stage were the key physiological basis in the evolution process of cotton cultivars from 1980s to 2000s for the cotton yield improvement within a short growing period., H. H. Luo, H. L. Zhang, Y. L. Zhang, W. F. Zhang., and Obsahuje bibliografii
Brassinosteroids (BRs), an important class of plant steroidal hormones, play a significant role in the amelioration of various biotic and abiotic stresses. 24-epibrassinolide (EBR), an active brassinosteroid, was applied exogenously in different concentrations to characterize a role of BRs in tolerance of melon (Cucumis melo L.) to high temperature (HT) stress and to investigate photosynthetic performance of HT-stressed, Honglvzaocui (HT-tolerant) and Baiyuxiang (HTsensitive), melon variety. Under HT, Honglvzaocui showed higher biomass accumulation and a lower index of heat injury compared with the Baiyuxiang. The exogenous application of 1.0 mg L-1 EBR, the most effective concentration, alleviated dramatically the growth suppression caused by HT in both ecotypes. Similarly, EBR pretreatment of HTstressed plants attenuated the decrease in relative chlorophyll content, net photosynthetic rate, stomatal conductance, stomatal limitation, and water-use efficiency (WUE), as well as the maximal quantum yield of PSII photochemistry (Fv/Fm), the efficiency of excitation capture of open PSII center, the effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching coefficient, and the photon activity distribution coefficients of PSI (α). EBR pretreatment further inhibited the increase in intracellular CO2 concentration, leaf transpiration rate, minimal fluorescence of dark-adapted state, nonphotochemical quenching, thermal dissipation, and photon activity distribution coefficients of PSII. Results obtained here demonstrated that EBR could alleviate the detrimental effects of HT on the plant growth by improving photosynthesis in leaves, mainly reflected as up-regulation of photosynthetic pigment contents and photochemical activity associated with PSI. and Y. P. Zhang ... [et al.].
Seedlings of Bidens cernua L. emerged when mean air temperature was 17.0±1.3 °C. The highest net photosynthetic rate (PN), 13.8±0.8 µmol(CO2) m-2 s-1, was monitored during the vegetative period (May-August), decreasing on an average by 50 % during flowering (August-September) and during fruiting (September-November) phases. The senescence phase (October-November) was characterised by 79, 58, and 18 % decrease of PN, chlorophyll content, and leaf area (LA), respectively, from the maximum values. The time span from seedling emergence to the end of fruiting phase was 202 d. The total plant biomass was 1.58±0.05 g of which 81 % was aboveground plant portion. The total dry mass relative growth rate averaged over the assimilation period was 0.0804±0.0002 kg kg-1 d-1, and it was correlated to both the net assimilation rate (NAR) and the leaf area ratio (LAR). and L. Gratani ... [et al.].
Hypobaria (low total atmospheric pressure) is essential in sustainable, energy-efficient plant production systems for long-term space exploration and human habitation on the Moon and Mars. There are also critical engineering, safety, and materials handling advantages of growing plants under hypobaria, including reduced atmospheric leakage from extraterrestrial base environments. The potential for producing crops under hypobaria and manipulating hypoxia (low oxygen stress) to increase health-promoting bioactive compounds is not well characterized. Here we showed that hypobaric-grown lettuce plants (25 kPa ≈ 25% of normal pressure) exposed to hypoxia (6 kPa pO2 ≈ 29% of normal pO2) during the final 3 d of the production cycle had enhanced antioxidant activity, increased synthesis of anthocyananins, phenolics, and carotenoids without reduction of photosynthesis or plant biomass. Net photosynthetic rate (PN) was not affected by total pressure. However, 10 d of hypoxia reduced PN, dark respiration rate (RD),
PN/RD ratio, and plant biomass. Growing plants under hypobaria and manipulating hypoxia during crop production to enhance health-promoting bioactive compounds is important for the health and well-being of astronauts exposed to space radiation and other stresses during long-term habitation. and C. He ... [et al.].
a1_We compared the interactive effects of temperature and light intensity on growth, photosynthetic performance, and antioxidant enzyme activity in Zizania latifolia Turcz. plants in this study. Plants were grown under field (average air temperature 9.6-25°C and average light intensity 177-375 W m-2) or greenhouse (20-32°C and 106-225 W m-2) conditions from the spring to the early summer. The results indicated that greenhouse-grown plants (GGP) had significantly higher plant height, leaf length, and leaf width, but lower leaf thickness and total shoot mass per cluster compared with field-grown plants (FGP). Tiller emergence was almost completely suppressed in GGP. Significantly higher chlorophyll (Chl) content and lower Chl a/b ratio were observed in GGP than in FGP. From 4 to 8 weeks after treatment (WAT), net photosynthetic rate (PN) was significantly lower in FGP than in GGP. However, from 9 to 12 WAT, PN was lower in GGP, accompanied by a decrease in stomatal conductance (gs) and electron transport rate (ETR) compared with FGP. Suppressed PN in GGP under high temperature combined with low light was also indicated by photosynthetic photon flux density (PPFD) response curve and its diurnal fluctuation 10 WAT. Meanwhile, ETR in GGP was also lower than in FGP according to the ETR - photosynthetically active radiation (PAR) curve. The results also revealed that GGP had a lower light saturation point (LSP) and a higher light compensation point (LCP). From 4 to 8 WAT, effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching (qP), and ETR were slightly lower in FGP than in GGP. The activities of ascorbate peroxidase (APX), guaiacol peroxidase (POD), glutathione reductase (GR), superoxide dismutase (SOD), and malondialdehyde (MDA) content were significantly higher from 4 to 8 WAT, but lower from 10 to 12 WAT in FGP., a2_However, catalase (CAT) activity was significantly lower in FGP from 4 to 8 WAT. Our results indicated that the growth and photosynthetic performance of Z. latifolia plants were substantially influenced by temperature, as well as light intensity. This is helpful to understand the physiological basis for a protected cultivation of this crop., N. Yan ... [et al.]., and Obsahuje bibliografii
Changes of photosynthesis under blue light were examined in the ABA-overproducing 7B-1 mutant in tomato. Net photosynthetic rate (PN), stomatal conductance (gs), intrinsic water-use efficiency (WUEi) and chlorophyll (a+b) [Chl (a+b)] content in leaves of different insertion (1st, 4th and 9th ones) were measured in 5-, 7- and 9-week-old plants. PN, gs, and Chl (a+b) content were mostly similar in young leaves of 7B-1 and wild type (WT) plants. With the aging of leaves, a blue-light-induced increase in PN and gs to steady-state was delayed and steady-state values of PN and gs were lower in 7B-1 plants compared with WT. Steady-state values of WUEi were increased in 4th and 9th leaves of 7B-1 plants compared with WT. The results can be explained by the higher endogenous level of ABA in 7B-1 plants and their lower sensitivity to ABA in earlier growth stage., E. Ježilová ... [et al.]., and Obsahuje bibliografii
Net photosynthetic rate (PN), stomatal conductance (gS), transpiration rate (E), intercellular CO2 concentration (Ci), leaf water potential (Ψw), leaf area, chlorophyll (Chl) content, and the activities of photosynthetic carbon reduction cycle (PCR) enzymes in two mulberry (Morus alba L.) cultivars (drought tolerant Anantha and drought sensitive M-5) were studied during water stress and recovery. During water stress, PN, gS, and E declined whereas Ci increased. PN, gS, and E were less affected in Anantha than in M-5, which indicates tolerance nature of Anantha over M-5. Activities of ribulose-5-phosphate kinase, NAD- and NADP-glyceraldehyde-3-phosphate dehydrogenases, and 3-phosphoglycerate kinase decreased with increasing stress in both the cultivars. The enzyme activities less affected in tolerant (Anantha) than in sensitive cultivar (M-5) were restored after re-watering to almost initial values in both the cultivars. Re-watering of the plants led to an almost complete recovery of PN, E, and gS, indicating that a short-term stress brings about reversible effect in these two cultivars of mulberry. and S. Thimmanaik ... [et al.].
Due to anthropogenic influences, solar UV-B irradiance at the earth's surface is increasing. To determine the effects of enhanced UV-B radiation on photosynthetic characteristics of Prunus dulcis, two-year-old seedlings of the species were submitted to four levels of UV-B stress, namely 0 (UV-Bc), 4.42 (UV-B1), 7.32 (UV-B2) and 9.36 (UV-B3) kJ m-2 d-1. Effects of UV-B stress on a range of chlorophyll (Chl) fluorescence parameters (FPs), Chl contents and photosynthetic gas-exchange parameters were investigated. UV-B stress promoted an increase in minimal fluorescence of
dark-adapted state (F0) and F0/Fm, and a decrease in variable fluorescence (Fv, Fv/Fm, Fv/F0 and F0/Fm) due to its adverse effects on photosystem II (PSII) activity. No significant change was observed for maximal fluorescence of dark-adapted state (Fm). Enhanced UV-B radiation caused a significant inhibition of net photosynthetic rate (PN) at UV-B2 and UV-B3 levels and this was accompanied by a reduction in stomatal conductance (gs) and transpiration rate (E). The contents of Chl a, b, and total Chl content (a+b) were also significantly reduced at increased UV-B stress. In general, adverse UV-B effects became significant at the highest tested radiation dose 9.36 kJ m-2 d-1. The most sensitive indicators for UV-B stress were Fv/F0, Chl a content and PN. Significant P<0.05 alteration in these parameters was found indicating the drastic effect of UV-B radiation on P. dulcis. and A. Ranjbarfordoei ... [et al.].
Differences in leaf traits among the dune species developing along the Latium coast were analysed. Cakile maritima Scop. subsp. maritima, Elymus farctus (Viv.) Runemark ex Melderis subsp. farctus, Ammophila arenaria (L.) Link subsp. australis (Mabille) Lainz, Ononis variegata L., Pancratium maritimum L., Eryngium maritimum L., and Anthemis maritima L. were considered. The considered species showed a similar net photosynthetic rate (PN) and chlorophyll content (Chl) during the year, with a peak from the end of April to the middle of May [13.0±3.6 μmol (CO2) m-2 s-1 and 0.63±0.21 mg g-1, respectively, mean values of the considered species], favoured by air temperature in the range 13.3-17.5°C, and 6% of soil water availability. In June-July, the increase of air temperature (Tmax = 28.4°C), associated with a lower water availability (42 mm, total rainfall of the period) and a 1% of soil water availability determined a significant decrease of P N (59%, mean of the considered species) and Chl (38%), and an increase of the carotenoid (Car)/Chl ratio (59%). The significant correlation between PN and stomatal conductance (gs) (p<0.05) explained 67% of P N variations. Moreover, the correlation between P N and leaf temperature (Tl) underlined that the favourable Tl enabling 90-100% of the highest PN for the considered species was within the range 23.4 to 26.6°C. P N decreased below half of its maximum value when Tl was over 35.8 and 37.4°C for E. farctus subsp. farctus and A. arenaria subsp. australis, respectively and over 32.2°C for the other considered species (mean value). Leaf mass area (LMA) varied from 6.8 ± 0.7 mg cm-2 (O. variegata) to 30.6 ± 1.6 mg cm-2 (A. arenaria). PCA (principal component analysis) carried out using the considered morphological and physiological leaf traits underlined that the co-occurring species were characterised by different adaptive strategies: E. farctus and A. arenaria photosynthesized for a long period also when air temperature was over 35.8 and 37.4°C, respectively, because of their lower transpiration rates [E, 1.4 ± 0.1 mmol (H2O) m-2 s-1], which seemed to be controlled by the highest LMA. On the contrary, A. maritima and C. maritima subsp. maritima had a higher PN (on an average 52% higher than the others) in the favourable period, allowed by the highest succulence index (SI, 85.7 ± 9 mg cm-2) and the lower LMA. The results allowed us to hypothesize that A. arenaria and E. farctus might be at a competitive advantage relative to the other considered species with respect to the increase of air temperature, by their ability to photosynthesize at sufficient rates also during summer. and L. Gratani, L. Varone, M. F. Crescente.
Two foxtail millet (Setaria italica L.) varieties were subjected to different shading intensity treatments during a grain-filling stage in a field experiment in order to clarify physiological mechanisms of low-light effects on the yield. Our results showed that the grain fresh mass per panicle, yield, photosynthetic pigment contents, net photosynthetic rate, stomatal conductance, effective quantum yield of PSII photochemistry, and electron transport rate decreased with the increase of shading intensity, whereas the intercellular CO2 concentration increased in both varieties. In addition, shading changed a double-peak diurnal variation of photosynthesis to a one-peak curve. In conclusion, the lower yield of foxtail millet was caused mainly by a reduction of grain mass assimilated, a decline in chlorophyll content, and the low photosynthetic rate due to low light during the grain-filling stage. Reduced light energy absorption and conversion, restricted electron transfer, and reduced stomatal conductance might cause the decrease in photosynthesis., X. Y. Yuan, L. G. Zhang, L. Huang, X. Qi, Y. Y. Wen, S. Q. Dong, X. E. Song, H. F. Wang, P. Y. Guo., and Obsahuje bibliografii