The Mediterranean climate of North Africa is characterized byuncertain rainfall immediately after seedling emergence, leadingto drought early in the growing season which depresses durumwheat production. However, there is limited understanding ofthe physiological basis of resistance of spring durum wheatto drought in rainfed Mediterranean regions. The objectivesof this study were to examine differences in some physiologicalcharacters among spring durum wheat cultivars in response toduration of early-season drought, and to determine the relationshipof these characters to drought resistance. In two field experiments(1995 and 1996 growing seasons) and a glasshouse experiment(1996), six spring sown durum wheat cultivars were evaluatedunder four water regimes: well irrigated and three differentwater deficits from emergence until the onset of tillering,mid-tillering or at the end of tillering. Cultivars differedin their response. Decreases in photosynthesis soon after droughtstress was imposed resulted mainly from reduced stomatal conductance.Continued water deficits also reduced mesophyll photosyntheticactivity. Possible factors determining the drought-resistanceof a cultivar are lower sensitivity of CO2exchange rate, netCO2uptake to water loss ratio, stomatal resistance, relativewater content and greater osmotic adjustment under stress. Furthermore,there is sufficient intraspecific variation in these physiologicalattributes to suggest their use as selection tools.Copyright1998 Annals of Botany Company Wheat;Triticum durumDesf.; early-season drought; physiological responses. 相似文献
The number of tumours developing on primary pinto bean leaves(Phaseolus vulgaris L. variety Pinto) inoculated with Agrobacteriumtumefaciens (Smith and Town.) Conn, strain B6, was increasedby as much as 100 per cent through the addition of several plant-growthfactors and antagonists of some of these factors to the freshlyinoculated leaves. Naphthylacetic acid, gibberellic acid, (2-chloroethyl)trimethylammonium chloride, and adenine gave a biphasic responsewith optimal promotions of tumour initiation at 10-5 to 10-4mg/ml. Tri-iodobenzoic acid and 4-chlorophenoxyisobutyric acidwere most active at 10-1 mg/ml. Mean tumour diameter showeda direct correlation with tumour number in these experiments.The results show tumour initiation to be sensitive to growthfactor changes, possibly through a heightened traumatic responseof the wounded leaves. The growth of the tumours was unaffectedby these additions except as they altered tumour number andthis secondarily affected tumour growth. 相似文献
A statistical method for analyzing sensory profiling data obtained by means of fixed vocabulary or free choice profiling is discussed. The most interesting feature of this method is that it involves only simple statistical treatment and can therefore be performed using standard software packages. The outcomes of this method are compared to those of Generalized Procrustes Analysis on the basis of two data sets obtained, respectively, by means of fixed vocabulary and free choice profiling. A significance test is also discussed in order to assess whether the overall configuration of the products is meaningful. This significance test is based upon a simulation study involving the permutation procedure. 相似文献
The vegetative growth of Dactylis glomerata L. in sand was studiedunder controlled light, temperature, and nutritional conditions.Plants were daily supplied with three nutrient solutions ofdifferent nitrate concentrations (102, 103 and2 x 104 mol I1). For each concentration, growthobeyed an exponential law between the fourth and seventh weeksafter sowing. The time constant of the exponential was the samefor the shoot as for the root, and showed no significant variationwith nitrate concentration. The kinetic results and the strong dependence of the root: shootratio on nitrate concentration are discussed on the basis ofThornley's model. Hypothesizing that the molecular mechanismsof nitrate absorption are independent of the nitrate concentrationof the nutrient solution, we derived a relationship betweenthe root: shoot ratio and nitrate concentration. This relationshipwas found to be compatible with the experimental results. Dactylis glomerata L., vegetative phase, kinetics of growth, root: shoot equilibrium, nitrate absorption 相似文献
Annual growth of the polar evergreen shrub Cassiope tetragona on Svalbard was evaluated as a proxy for Arctic summer temperatures. Transfer functions were derived from temperature‐growth correlations of shoots and from a temperature‐growth response, obtained from experimental warming using open top chambers (OTC) in high Arctic tundra vegetation at Isdammen approximately 1.5 km southeast of Longyearbyen, Svalbard (78°N, 15 E) and in Longyeardalen, 3 km west of Isdammen from 2004 to 2006. Air temperatures, monitored throughout the summer months, were 1.3 °C higher inside the OTCs than in the control plots. Annual stem growth was measured by tagging stems and leaves, and in the lab with shoots harvested from OTCs and control plots. Annual growth parameters assessed were leaf production, sum of length and weight of individual leaves, and stem length increment derived from leaf scar distances and the distances between wintermarksepta in the stem. Wintermarksepta are formed at the end of the summer growth period when the pith is narrowing and consist of dense and dark tissue ( Fig. 1b ). The variation of annual growth in a 34‐year site chronology (based on Cassiope shoots from the surroundings of the OTCs and control plots) correlated strongly with the mean summer temperature on Svalbard. The number of leaf pairs, leaf length and stem length also increased in the OTC warmed plots in the second and third year of warming. Transfer functions were derived from the temperature‐annual growth correlations from a single shoot from Longyeardalen, from the cross‐dated Isdammen site chronology and from the growth response to experimental warming. Based on leaf scar distances and distances between wintermarksepta of well‐preserved subfossil shoots in arctic tundra soil, annual stem length increase was assessed for the layers of a soil core collected at the Isdammen site. Based on the derived transfer functions summer temperature of the period relating to the 15 cm deep tundra soil core layer, radiocarbon dated at 4230±40 bp , may have been 3.0 °C lower than the present‐day 6.2 °C value. These results indicate that the transfer functions can be used to reconstruct past temperatures, beyond the time range of instrumental temperature and ice core records of Svalbard. Figure 1 Open in figure viewer PowerPoint (a) Morphology of shoot of Cassiope tetragona collected May 26, 2007, Longyeardalen. Removal of the front row of leaves shows four leaf pairs of the 2006 summer, the leaf primordium for the 2007 growing season and the stem length increase summer 2006. (b) Wintermarksepta, darker colored than the pith tissue, indicating the winterperiod in a longitudinal section of an air‐dried shoot collected August 26, 2006, Longyeardalen. 相似文献
Maize being sub-tropical crop is sensitive to water deficit during the
early growth stages; particularly clay-rich soil, due to the compaction of the soil.
It is well-documented that potential sub-surface drip irrigation (SDI) (Full irrigation; SDIFull (100% field capacity (FC)), Deficit irrigation; SDIDeficit (70% FC))
improves water use efficiency, which leads to increased crop productivity; since it
has a constraint that SDI excludes soil air around the root-zone during irrigation
events, which alter the root function and crop performance. Additionally, in clayrich soils, the root system of plants generally suffers the limitation of oxygen,
particularly the temporal hypoxia, and occasionally from root anoxia; while
SDI system accomplishes with the aerating stream of irrigation in the rhizosphere
could provide oxygen root environment. The oxygen can be introduced into the
irrigation stream of SDI through two ways: the venturi principle, or by using solutions of hydrogen peroxide through the air injection system. Therefore, the application of hydrogen peroxide (H2O2; HP) can mitigate the adverse effect of soil
compactness and also lead to improving the growth, yield and yield attributes
of maize in clay-rich soil. Considering the burning issue, a field study was conducted in consecutive two seasons of 2017 and 2018; where hybrid maize was
cultivated as a second crop, to evaluate the effect of liquid-injection of H2O2
(HP) into the irrigation stream of SDI on the performance of maize in a clay-rich
soil field of Adana, Turkey. When soil water content decreased in 50% of available water, irrigation was performed. The amount of water applied to reach the
soil water content to the field capacity is SDIFull (100% FC) and 70% FC of this
water is SDIDeficit (70% FC). In the irrigation program, hydrogen peroxide (HP)
was applied at intervals of 7 days on average according to available water with
and without HP: SDIFull (100% FC) + 0 ppm HP with full SDI irrigation;
SDIFull (100% FC) + 250 ppm HP with deficit SDI irrigation; SDIDeficit
(70% FC) + 0 ppm HP, SDIDeficit (70% FC) + 250 ppm HP and SDIDeficit
(70% FC) + 500 ppm HP. Deficit irrigation (SDIDeficit (70% FC)) program
was started from tasseling stage and continued up to the physiological maturity
stage with sub-soil drip irrigation. H2O2 was applied 3 times during the growing season. Two years’ results revealed that the liquid-injection of H2O2 into the irrigation stream of SDI improved the growth and yield-related attributes and grain
yield of maize. Based on the obtained results, during the extreme climatic condition in the year 2017, SDIFull (100% FC) + 250 ppm HP was more effective than
SDIFull (100% FC) + 0 ppm HP on all traits for relative to full irrigation. While,
during the favourable climatic condition in the 2018 season, SDIFull (100% FC)
+ 250 ppm HP was more effective than full irrigation with SDIFull (100% FC) +
0 ppm HP for the grain yield, grains, and SPAD value. Accordingly, the most
effective treatment was SDIFull (100% FC) + 250 ppm HP, as it gave the highest
growth and yield-related attributes and grain yield of maize followed by
SDIDeficit (70% FC) + 250 ppm HP. Therefore, SDIFull with 250 ppm H2O2
using as liquid-injection may be recommended to mitigate the adverse effect of
soil compactness particularly water-deficit stress in clay-rich soil for the sustainability of maize production. 相似文献