A fíeld experiment was conducted to evaluate the effects of Cu and Pb on photosynthesis and growth characteristics of oats. The plants grown on the site with elevated levels of Cu-Pb were reduced in height and biomass, compared to control plants, and appeared chlorotic while the accumulations of both Cu and Pb in the above-ground parts were in the range considered to be phytotoxic. Cu and Pb led to a pronounced reduction (47 %) of chlorophyll (Chl) (a + b) content, accompanied by proportional changes in ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity. Hence Cu and Pb effects did not result in the destruction of the photosynthetic apparatus but in its coordinated reduction. Growth at the heavy metal contaminated site resulted in a decreased (7 %) quantum yield of photochemistry in photosystem 2 (PS2), as given by the ratio Fy/Fn, measured in dark adapted leaves in the field. The half-rise time (ti/2) from the initial (Fq) to maximal (F^) Chl fluorescence was increased, suggesting that the amount of active pigments associated with the photochemical apparatus decreased and that the functional Chl antennae size of the photosynthetic apparatus was smaller compared to the control plants. Although Cu and Pb affected the photosynthetic apparatus in multiple ways, the prevailing effect was that on RuBPCO activity, which in tum must háve limited the overall photosynthetic activity.
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.].
Fifty-day old plants of Capsicum anmmm L, with two developed leaves were placed into controlled environment chambers at atmospheric (350 cm^ m'^, ACO2) and elevated (700 cm^ m-^, ECO2) CO2 concentrations under different nitrogen and water supply. Plant response to ECO2 and the modulating effect of the availability of nitrogen and water were evaluated. CO2 effects were significant only after 40 d of treatment, An increase in plant growth and yield was found in ECO2 plants only under a good supply of both water (HW) and nitrogen (HN). Chlorophyll concentration responded only to N supply. Root/shoot ratio was higher under ECO2 only under low N (LN) and low water (LW) supply. Leaf area and specific leaf area decreased under ECO2. Flowering and fructification took plače earlier in ECO2 under FIN and FIW. Thus, all CO2 effects were modulated by the N and water supply and the duration of exposure.
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.].
To determine the effects of rootstock choice on the scion response to drought stress, we compared the vegetative growth, biomass accumulation, gas exchange, and water-use efficiency (WUE) of ‘Gale Gala’ apple (Malus domestica Borkh.) trees grafted onto nine wild Chinese Malus rootstocks. Compared with the well-watered control, drought treatment limited growth, as manifested by smaller increments in plant height (PH), trunk diameter (TD), total fresh biomass (TB), total dry biomass (TDB), total leaf area (LA), and relative growth rate (RGR). The extent of this effect differed among rootstocks. Stress conditions led to increases in the root/shoot ratio (RSR), leaf thickness (LT), water-holding capacity (WHC), carbon isotope composition (δ13C), and WUE. Decreases were noted in stomatal density (SD), leaf relative water content (RWC), chlorophyll content (Chl), net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs), again varying by rootstock. Those that are generally considered more drought-tolerant, e.g., M. sieversii, M. prunifolia, and M. toringoides, had smaller declines in PH, TD, TB, TDB, LA, RGR, SD, RWC, Chl, PN, E, and gs and proportionally greater increases in RSR, LT, WHC, δ13C, and WUE compared with the droughtsensitive M. hupehensis and
M. sieboldii. These results suggest that moisture stress has a significant dwarfing effect in the latter two species. Based on WUE calculations, trees on drought-tolerant rootstocks showed higher tolerance when stressed, whereas those on drought-sensitive rootstocks were less tolerant, as indicated by their lower WUE values., B. H. Liu ... [et al.]., and Obsahuje bibliografii
A hydroponic, greenhouse experiment was conducted to assess the effects of NaCl on growth, gas-exchange parameters, chlorophyll (Chl) content, and ion distribution in seven sesame (Sesamum indicum L.) genotypes (Ardestan, Varamin, Naz-Takshakhe, Naz-Chandshakhe, Oltan, Yekta, Darab). The plants were grown in 4-L containers and subjected to varying levels of salinity (0, 30, and 60 mM NaCl). After 42 days, salt treatments induced decreases of plant fresh and dry mass, total leaf area, and plant height in all genotypes. Increasing NaCl concentration caused significant, genotypedependent decrease in the net photosynthetic rate, stomatal conductance, Chl content, and maximum quantum efficiency of photosystem II, while it increased the intercellular CO2 concentration. Based on the dry matter accumulation under salinity, the genotypes were categorized in two groups, i.e., salt-tolerant and salt-sensitive. The impact of salt on plant ion concentrations differed significantly among the sesame genotypes and between both two groups. The plant Na+ concentrations were significantly lower in Ardestan, Darab, and Varamin genotypes than those found in the remaining genotypes. The highest plant K+ and Ca2+ concentrations together with the lowest Na+/K+ and Na+/Ca2+ ratios were observed in Ardestan, Varamin, and Darab genotypes. Our results indicated the presence of differences in salt response among seven sesame genotypes. It suggested that growth and photosynthesis could depend on ion concentrations and ratios in sesame., A. H. Bazrafshan, P. Ehsanzadeh., and Obsahuje bibliografii
Acclimation to irradiance was investigated in seedlings of Japanese beech {Fagus crenata Bl.) grown under one of five irradiance regimes for three years. Inadiance (/) regimes covered the range of environmental conditions which this species normally would experience in Japanese beech forests: exposed [22.1 mol(quantum) m‘2 d'*, matching mean daily irradiance of exposed canopies], partially shaded [8.8, 2.7 and 1.5 mol(quantum) d'*, respectively, comparable to various midcanopies], and deeply shaded [0.5 mol(quantum) nu^ d"', equivalent to forest floor], There were consistent strong relationships between irradiance, growth performance and net photosynthetic rate (P^) for this species. Greater growth performance and were achieved as / increased, with aboveground height growth increasing as rapidly as basal diameter growth. This tiend was also observed in the leaf specific mass and leaf nitrogen content. Exposed plants had higher saturation I for (> 1400 |amol m'^ s‘*) than partially shaded plants (1180, 1100 and 753 pmol m‘2 s'', respectively). Higher leaf conductance, leaf specific mass and leaf nitrogen content correlated positively with higher Nevertheless, the beech seedlings adapted to deep shade by producing more total chlorophyll and requiring lower compensation / (Qq) at lower growth irradiances. Seedlings of Japanese beech were very tolerant to shade but capable of acclimating to strong I. Thus / is an important factor influencing growth and photosynthetic capacity of Japanese beech.
The effects of intra- and interspecific competition on growth, net photosynthetic rate (/^n), intemal CO2 concentration (cj), leaf conductance to CO2 (gi), and xylem leaf water potentials Q¥) were investigated among well-watered seedlings of the old-field species Abutilon theophrasíi. Ambrosia tri/ida, and Helianíhus annuus. In all comparisons, *F values of the target plants were unaffected by the presence of neighbors. On the other hand, revealed inhibitory effects of neighbors on A. theophrasíi and H. annuus. The above- and belowground biomass of all species was reduced in the presence of neighbors. Hence both inter- and intraspecific competition among seedlings may be important in influencing community stiucture in old-field communities.