We investigated the responses of photon-saturated photosynthesis rate (Psat) and its simultaneous acclimation of anatomy and nitrogen use patterns of current needles of Korean pine (Pinus koraiensis) seedlings grown under factorial combinations of two nitrogen levels and irradiances. Although N supply resulted in a significant increase of N content in needles under both irradiances, the increase of P sat tended to be suppressed only in shade (S). The significant increase of P sat in full sunlight (O) was associated with the increase of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and chlorophyll (Chl) contents. In contrast, small increase of Chl content and no increase of RuBPCO content were found in S (90 % cut of full irradiance), which would result in a small increase of Psat. This result suggests that extra N is stocked in needles under shade for the growth in next season. With N supply, a significant decrease of specific leaf area (SLA) was detected only in O. This decrease of SLA was due to the increase of density of needle. Furthermore, the increase of needle density was not due to the increased number and size of mesophyll cells, but the increased density of each mesophyll cell. Therefore, although SLA changed in O, the change did not involve anatomical adaptation to use increased N effectively, at least observable by light microscopy. Hence, even though the SLA would change, N deposition will improve the photosynthetic capacity of Korean pine seedlings, not through the development of needle anatomy but through improvement of the allocation of N in both irradiances. and K. Makoto, T. Koike.
The effects of nitrogen (N) supply restriction on the CO2 assimilation and photosystem 2 (PS2) function of flag leaves were compared between two contrastive Japanese rice cultivars, a low-yield cultivar released one century ago, cv. Shirobeniya (SRB), and a recently improved high-yield cultivar, cv. Akenohoshi (AKN). Both cultivars were solution-cultured at four N supply levels from N4 (control) to N1 (the lowest). With a reduction in N-supply, contents of N (LNC), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), and chlorophyll (Chl) in flag leaves decreased in both cultivars. In parallel with this, the net photosynthetic rate (PN), mesophyll conductance (g m), and stomatal conductance (gs) decreased. PN was more dominantly restricted by gm than gs. The values of PN, gm, and RuBPCO content were larger in AKN than SRB at the four N supply levels. The content of Chl greatly decreased with N deficiency, but the reduction in the maximum quantum yield of PS2 was relatively small. Quantum yield of PS2 (ΦPS2) decreased with N deficiency, and its significant cultivar difference was observed between the two cultivars at N1: a high value was found in AKN. The content ratio of Chl/RuBPCO was also significantly low in AKN. The low Chl/RuBPCO is one of the reasons why AKN maintained a comparatively high PN and ΦPS2 at N deficiency. The adequate ratio of N distribution between Chl and RuBPCO is the important prerequisite for the efficient and sustainable photosynthesis in a flag leaf of rice plant under low N-input. and E. Kumagai, T. Araki, F. Kubota.
Environmental conditions play a major role for effects of olive mill wastewater (OMW) application to soil. Choosing a different season for OMW application than the commonly practiced winter, may help avoid negative effects. However, understanding of the OMW-soil interaction during different seasons is still incomplete due to the lack of comparative data. In this study, an 18 months field experiment was carried out in an olive orchard in West Bank. Degree and persistence of soil salinization, acidification, accumulation of phenolic compounds and soil water repellency were investigated as a function of soil depth and time elapsed after OMW application, which was performed either in spring, summer (with and without irrigation) or winter. The persistence of negative effects increased with duration of the hot and dry period following the application due to accumulation and polymerization of OMW. On the other hand, leaching of OMW components to groundwater is favored during the rainy season and by formation of preferential flow paths before the rain season starts. The risks of groundwater contamination and persistent negative effects decrease with increasing time under conditions favoring biological activity. Therefore, OMW application in spring if improved by a careful irrigation is considered as the most suitable under semiarid conditions for clay loam soils.
Leaf water potential, leaf osmotic potential, chlorophyll a and b contents, stomatal conductance, net photosynthetic rate, and water use efficiency were determined in two pistachio species (Pistacia khinjuk L. and P. mutica L.) grown under osmotic drought stress induced by a combination of NaCl and polyethylene glycol 6000. A decrease in values for all mentioned variables was observed as the osmotic potential of the nutrient solution (Ψs) decreased. The osmotic adjustment (ΔΨπ) of the species increased by decreasing Ψs. Thus P. khinjuk had a higher osmotic drought stress tolerance than P. mutica. and A. Ranjbarfordoei ... [et al.].
Abscisic acid (ABA), an important chemical signal from roots, causes physiological changes in leaves, including stomata closure and photoprotection. Furthermore, endogenous ABA concentration in leaves and stomatal behavior vary with the species adapted to different water regimes. In this study, Ficus microcarpa, a hemiepiphyte, Salix warburgii, a hygrophyte, and Acacia confusa, a mesophyte, were used to elucidate the effects of leaf detachment on photosystem II (PSII) efficiency under osmotic- and high-light stresses. Results indicate that, under osmotic- and high-light stresses, PSII efficiency of the detached leaves was lower than that of the attached leaves for all three tree species, when compared at the same levels of stomatal resistance and leaf water potential. Exogenous ABA could mitigate the PSII efficiency decrease of detached F. microcarpa leaves under osmotic- and high-light stresses. Yet, the osmotic stress could raise endogenous ABA concentration in the attached, but not in the detached F. microcarpa leaves. In addition, partial root-zone drying exerted a significant effect on stomatal behavior but not on the water status of F. microcarpa leaves. These observations imply that the stronger ability of PSII in the attached leaves of F. microcarpa under osmoticand high-light stresses was probably due to the protective action of ABA from roots. On the contrary, endogenous ABA level of S. warburgii leaves was very low. In addition, partial root-zone drying produced no significant effect on its stomatal behavior. Therefore, PSII in attached S. warburgii leaves was possibly protected from the damaging effects of excess absorbed energy by signals other than ABA, which were transported from the roots. and J.-H. Weng ... [et al.].
Little is known about the response of trees to elevated ozone (O3) in the subtropical region of China, where ambient O3 concentrations are high enough to damage plants. In this study, pigment content, gas exchange and chlorophyll (Chl) a fluorescence in leaves of Liriodendron chinense (Hemsl.) Sarg seedlings, a deciduous broadleaf tree species native in subtropical regions, were investigated at 15, 40, and 58 days after O3 fumigation (DAF) at a concentration of 150 mm3 m-3 (E-O3). At the end of experiment, seedlings were harvested for biomass measurement. E-O3 caused visible injuries on the mature leaves e.g. necrotic patches and accelerated early defoliation. Relative to the charcoal-filtered air (CF) treatment, E-O3 significantly decreased shoot and root biomass, pigment content, light-saturated net photosynthesis (P Nsat), stomatal conductance (gs), maximum rate of carboxylation (Vcmax), photochemical quenching coefficient (qp) and effective quantum yield of PSII photochemistry (ΦPSII), and also caused a slight reduction in relative increase of basal diameter. Therefore, L. chinense can be assumed to be an O3-sensitive tree species, which will be threatened by increasing ambient O3 concentrations in China. and W. W. Zhang ... [et al.].
Seedlings of spring barley, meadow fescue, and winter rape were fumigated with 180 μg kg-1 of ozone for 12 d, and effect of O3 on photosynthesis and cell membrane permeability of fumigated plants was determined. Electrolyte leakage and chlorophyll fluorescence were measured after 6, 9, and 12 d of fumigation, while net photosynthetic rate (PN) and stomatal conductance (gs) were measured 9 d after the start of ozone exposure. O3 treatment did not change membrane permeability in fescue and barley leaves, while in rape a significant decrease in ion leakage was noted within the whole experiment. O3 did not change the photochemical efficiency of photosystem 2 (PS2), i.e., Fv/Fm, and the initial fluorescence (F0). The values of half-rise time (t1/2) from F0 to maximal fluorescence (Fm) decreased in fescue and barley after 6 and 9 d of fumigation. PN decreased significantly in ozonated plants, in the three species. The greatest decrease in PN was observed in ozonated barley plants (17 % of the control). The ozone-induced decrease in PN was due to the closure of stomata. Rape was more resistant to ozone than fescue or barley. Apparently, the rape plants show a large adaptation to ozone and prevent loss of membrane integrity leading to ion leakage. and A. Plażek, M. Rapacz. A. Skoczowski.
Salt stress is one of the most critical factors hindering the growth and development of plants. Paclobutrazol (PBZ) is widely used to minimize this problem in agriculture because it can induce salt stress tolerance in plants. This study investigated the effects of PBZ on salt tolerance of seedlings from two Chinese bayberry cultivars (i.e., Wangdao and Shenhong). Plants were treated with three salt concentrations (0, 0.2, and 0.4 % NaCl) and two PBZ concentrations (0 and 2.0 μmol L-1). Application of PBZ increased a relative water content, proline content, chlorophyll (a+b) content, and antioxidant enzyme activities in both cultivars, resulting in a better acclimation to salt stress and an increase in dry matter production. We concluded that PBZ ameliorated the negative effects of salt stress in Chinese bayberry seedlings., Y. Hu, W. Yu, T. Liu, M. Shafi, L. Song, X. Du, X. Huang, Y. Yue, J. Wu., and Obsahuje bibliografii
In this paper simulated rainfall experiments in laboratory were conducted to quantify the effects of patchy distributed Artemisia capillaris on spatial and temporal variations of the Darcy-Weisbach friction coefficient (f). Different intensities of 60, 90, 120, and 150 mm h-1 were applied on a bare plot (CK) and four different patched patterns: a checkerboard pattern (CP), a banded pattern perpendicular to slope direction (BP), a single long strip parallel to slope direction (LP), and a pattern with small patches distributed like the letter ‘X’ (XP). Each plot underwent two sets of experiments, intact plant and root plots (the above-ground parts were removed). Results showed that mean f for A. capillaris patterned treatments was 1.25-13.0 times of that for CK. BP, CP, and XP performed more effectively than LP in increasing hydraulic roughness. The removal of grass shoots significantly reduced f. A negative relationship was found between mean f for the bare plot and rainfall intensity, whereas for grass patterned plots fr (mean f in patterned plots divided by that for CK) increased exponentially with rainfall intensity. The f -Re relation was best fitted by a power function. Soil erosion rate can be well described using f by a power-law relationship.