Black cumin (Nigella sativa L.) seeds were surface-sterilized and soaked for 5, 10, or 15 h in 1, 10, or 100 μM aqueous solution of kinetin (KIN). The potted plants were then analyzed at 30, 50, and 70 days after emergence (DAE) for dry mass (DM), leaf area (LA), chlorophyll (Chl) content, stomatal conductance (g s), carbonic anhydrase (CA), and nitrate reductase (NR) activity, total protein content, and net photosynthetic rate (PN). Capsule number and seed yield were determined at harvest (90 DAE). Treatment with the growth regulator was found to appreciably enhance all the determinants, with most prominent results being obtained following 10-h soaking with 10 μM KIN, in which case the values for DM, LA,
PN, CA and NR activity, and seed yield were elevated by 55, 63, 43, 38, 29, and 23% respectively over the control at the 50-day stage. and S. H. Shah.
In this study, we questioned whether ground-level ozone (O3) induces hormesis in Japanese larch (Larix kaempferi) and its hybrid F1 (L. gmelinii var. japonica × L. kaempferi). In order to answer the question, we exposed seedlings of both taxa to four O3 treatments [ranging from ≈10 to 60 nmol(O3) mol-1] in open-top chambers for two consecutive growing seasons. We found a hormetic response in maximum photosynthetic rate (PNmax) at 1700 μmol(CO2) mol-1 and maximum rates of carboxylation (Vcmax) and electron transport (Jmax) in both larches. Stimulation of PNmax, Vcmax, and Jmax did not lead to suppressed plant productivity in Japanese larch, which followed a stress-tolerant strategy, but it did lead to suppressed plant productivity in hybrid larch which followed a competitive strategy. These findings are the first to suggest that stimulation of physiological functions by low O3 exposures may have negative consequences for larch reproduction., T. Sugai, D.-G. Kam, E. Agathokleous, M. Watanabe, K. Kita, T. Koike., and Obsahuje bibliografii
Seedlings from four provenances of Jatropha curcas were subjected to 80, 50, and 30% of soil field capacity in potted experiments in order to study their responses to water availability. Our results showed that with the decline of soil water availability, plant growth, biomass accumulation, net photosynthetic rate, stomatal conductance (gs), and transpiration rate (E) decreased, whereas leaf carbon isotope composition (δ13C), leaf pigment contents, and stomatal limitation value increased, while maximal quantum yield of PSII photochemistry was not affected. Our findings proved that stomatal limitation to photosynthesis dominated in J. curcas under low water availability. The increase of δ13C should be attributed to the decrease in gs and E under the lowest water supply. J. curcas could adapt to low water availability by adjusting its plant size, stomata closure, reduction of E, increasing δ13C, and leaf pigment contents. Moreover, effects of provenance and the interaction with the watering regime were detected in growth and many physiological parameters. The provenance from xeric habitats showed stronger plasticity in the plant size than that from other provenances under drought. The variations may be used as criteria for variety/provenance selection and improvement of J. curcas performance., C. Y. Yin, X. Y. Pang, A. D. Peuke, X. Wang, K. Chen, R. G. Gong., and Seznam literatury
a1_Attention should be paid to ozone (O3) sensitivity of greening plant since ground-level O3 concentrations are increasing especially in urban and suburban area. We studied the ecophysiological responses to elevated O3 of four shrub species [Euonymus bungeanus Maxim. (EB), Photinia × fraseri (PF), Chionanthus retusus Lindl. & Paxt. (CR) and Cornus alba L. (CA)], which are often used for garden greening in China. Saplings of those species were exposed to high O3 concentration (70 nmol mol-1, 7 h d-1 for 65 d) in open-top growth chambers. Responses to O3 were assessed by gas exchanges, chlorophyll (Chl) fluorescence and dry mass. We found that elevated O3 significantly decreased lightsaturated net photosynthetic rate (PNsat), transpiration rate (E) and stomatal conductance (gs). The ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) did not reduce under O3 fumigation which suggested that the O3-induced depressions of P Nsat under O3 fumigation were probably due to limitation of mesophyll processes rather than stomatal limitation. High O3 exposure also significantly depressed the maximum efficiency of photosystem II (PSII) photochemistry in the dark-adapted state (Fv/Fm) which meant the O3-induced photoinhibition. Both root dry mass and root/shoot ratios were significantly decreased under ozone fumigation, but the total mass was unchanged. The responses of gas exchange such as PNsat in these four shrubs to O3 exposure were species-specific. Highest loss of PNsat was observed in EB (-49.6%), while the CR had the lowest loss (-36.5%). Moreover, the O3-exposed CR showed similar gs as CF, reflecting that its O3 flux might be unchanged under elevated O3 environment. Ozone drastically decreased actual quantum yield of PSII (ΦPSII) and electron transport rate (ETR) in EB while increased ΦPSII and ETR in CR., a2_Furthermore, the relative losses in P Nsat positively correlated with the relative decreases in ΦPSII and ETR which indicated that the impairment of photosynthesis was probably affected by the light reaction process. The light reaction of EB was impaired most seriously but that of CR was not damaged. All results indicated that EB was probably the most sensitive shrub species to O3 while CR the most tolerant one. Therefore, CR might be an ideal choice for greening in ozone-polluted areas., L. Zhang ... [et al.]., and Obsahuje bibliografii
Intercropping, a traditional and worldwide cropping practice, has been considered as a paradigm of sustainable agriculture based on complementary mechanisms among different crop species. Soybean (Glycine max) is widely relay intercropped about 60 days before maize (Zea mays) harvest in Southwest China. However, shade caused by tall maize plants may be a limiting factor for soybean growth at a seedling stage. In field research, we studied the ecophysiological responses of two widely cultivated soybean varieties [Gongqiudou494-1 (GQD) and Gongxuan 1 (GX)] to maize shading in a relay intercropping system (RI) compared with monocropped soybean plants (M). Our results showed that soybean seedlings intercropped with maize exhibited significantly downregulated net photosynthetic rate (PN) (-38.3%), transpiration rate (-42.7%), and stomatal conductance (-55.4%) due to low available light. The insignificant changes in intercellular CO2 concentration and the maximum efficiency of PSII photochemistry suggested that the maize shading-induced depressions in PN were probably caused by the deficiency of energy for carbon assimilation. The significantly increased total chlorophyll (Chl) content (+27.4%) and Chl b content (+52.2%), with lowered Chl a/b ratios (-20.5%) indicated soybean plants adjusted their light-harvesting efficiency under maize shading condition. Biomass and leaf area index (LAI) of seedlings under RI decreased significantly (-78.7 and -71%, respectively) in comparison with M. Correlation analysis indicated the relative reduction in biomass accumulation was caused by the decline in LAI rather than PN, it affected negatively the final yields of soybean (32.8%). Cultivar-specific responses to maize shading were observed in respects of LAI, biomass, and grain yield. It indicated that GX might be a better cultivar for relay intercropping with maize in Southwest China., B. Y. Su, Y. X. Song, C. Song, L. Cui, T. W. Yong, W. Y. Yang., and Obsahuje bibliografii
a1_Low light availability under a forest canopy often limits plant growth; however, sudden increase in light intensity may induce photoinhibition of photosynthesis. The aim of this study was to evaluate the ecophysiological changes that occur in potted plants of Minquartia guianensis and Swietenia macrophylla during the acclimation process to full sunlight. We used six full-sun independent acclimation periods (30, 60, 90, 120, 150, and 180 days) and a control kept in the shade. Shading was obtained by placing plants under the canopy of a small forest. The Fv/Fm ratio, net photosynthetic rate (PN), the maximum carboxylation velocity of Rubisco (Vcmax), maximum electron transport rate (Jmax), specific leaf area (SLA), and growth were assessed at the end of each of the six acclimation periods. Plant exposure to full sunlight caused a sudden decrease in the Fv/Fm ratio (photoinhibition) particularly in Minquartia. Photooxidation (necrotic patches) of the leaf tissue was observed in upper leaves of Minquartia. The higher PN values were observed in Swietenia under full sun, about 12 μmol(CO2) m-2 s-1. Vcmax25 values were higher after 90 days of acclimation, about 14 μmol(CO2) m-2 s-1 for Minquartia, and 35 μmol(CO2) m-2 s-1 for Swietenia. At the end of a 180-d acclimation period Jmax25 was 35 μmol(electron) m-2 s-1 for Minquartia and 60 μmol(electron) m-2 s-1 for Swietenia. SLA was higher in Swietenia than in Minquartia. In Minquartia, monthly rate of leaf production per plant (MRLP) was positive (0.22 leaf month-1) after four months in the open. Whereas, in Swietenia MRLP was positive (0.56 leaf month-1) after an acclimation period of two months. After six months in the open, height growth rates were 3.5 and 28 mm month-1 for Minquartia and Swietenia, respectively., a2_The greater acclimation capacity of Swietenia was associated to an enhanced photosynthetic plasticity under full sun. In Minquartia, transition to full-sun conditions and lack of physiological adjustment resulted in severe photoinhibition and loss of leaves., G. F. C. Azevedo, R. A. Marenco., and Obsahuje bibliografii
Plants are able to acclimate to their growth light environments by utilizing a number of short- and long-term mechanisms. One strategy is to prevent accumulation of excess reactive oxygen species that can lead to photoinhibition of photosynthesis. Ureides, generated from purine degradation, have been proposed as antioxidants and involved in certain abiotic stress responses. Eutrema salsugineum (Thellungiella salsuginea) is an extremophilic plant known to exhibit a high degree of tolerance to a variety of abiotic stresses that invariably generate reactive oxygen species. In the present study we have investigated the possible role of the ureide metabolic pathway during acclimation to growth irradiance and its conference of tolerance to photoinhibition in Eutrema. Ureide accumulation was greater under high light growth which also conferred tolerance to photoinhibition at low temperature as measured by the maximal quantum yield of PSII photochemistry. This may represent an adaptive plastic response contributing to the extreme tolerance exhibited by this plant. Our results would provide evidence that ureide accumulation may be involved in abiotic stress as another defence mechanism in response to oxidative stress., V. M. Malik, J. M. Lobo, C. Stewart, S. Irani, C. D. Todd, G. R. Gray., and Obsahuje seznam literatury
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.].
The effect of elevated carbon dioxide (600±50 cm3 m-3; C600) on growth performance, biomass production, and photosynthesis of Cenchrus ciliaris L. cv. 3108 was studied. This crop responded significantly by plant height, leaf length and width, and biomass production under C600. Leaf area index increased triple fold in the crops grown in the open top chamber with C600. The biomass production in term of fresh and dry biomass accumulation increased by 134.35 (fresh) and 193.34 (dry) % over the control (C360) condition where the crops were grown for 20 d. The rate of photosynthesis and stomatal conductance increased by 24.51 and 46.33 %, respectively, in C600 over C360 plants. In comparison with C360, the rate of transpiration decreased by 6.8 % under C600. Long-term exposure (120 d) to C600 enhanced photosynthetic water use efficiency by 34 %. Also the contents of chlorophylls a and b significantly increased in C600. Thus C. ciliaris grown in C600 throughout the crop season may produce more fodder in terms of green biomass. and R. K. Bhatt, M. J. Baig, H. S. Tiwari.
The combination of two scion-one rootstock was used for two apple cultivars, ‘Pink Lady’ and ‘Qinguan’, budded on the same, one-year-old Malus hupehensis (Pamp.) Rehd. to reduce the impact of root and pot size and in order to understand the growth, water-use efficiency (WUE), and chlorophyll fluorescence characteristics. The two-scion grafted trees were planted in plastic pots under two water regimes, i.e. 70% field capacity (FC) and 55% FC. Results indicated that different scions were affected differently by drought stress. ‘Pink Lady’ had higher net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) compared with ‘Qinguan’ under both water treatments. However, ‘Qinguan’ had lower minimal fluorescence (F0), higher maximum fluorescence (Fm), and higher maximum photochemical efficiency of photosystem II (Fv/Fm) than ‘Pink Lady’ at 55% FC. Moreover, ‘Qinguan’ had larger shoot dry mass (ShDM) and higher intrinsic WUEI than ‘Pink Lady’ under both water status. Gas-exchange and growth parameters, except for PN and scion diameter, were significantly affected by the cultivar and water treatment. At 70% FC, ShDM was significantly correlated with WUEI. Moreover, WUEI was negatively linearly correlated with g s at either 70 or 55% FC. These results might indicate that ‘Pink Lady’ was more sensitive to drought than ‘Qinguan’. ‘Qinguan’ apple was able to improve WUE more than ‘Pink Lady’ under both well-watered and drought conditions. The growth parameters and photosynthetic capacity of two different scions showed that the combination of double
scion-one rootstock might eliminate the influences of the rootstock and pot size. and X. P. Sun ... [et al.].