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121.
In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration
rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth
courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area
growth curve was 0.155–0.175 day−1, while that for the weight growth was 0.112–0.117 day−1. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm2 g−1 and then decreased until it leveled off at about 140 cm2g−1. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I
0) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I
0)+B andb=C/(I′/I
0)+D. Leaf respiration rate was also increased with increasingI′/I
0. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear
regression on semilogarithmic co-ordinates. 相似文献
122.
Summary As clonal plants grow they move through space. The movement patterns that result can be complex and difficult to interpret without the aid of models. We developed a stochastic simulation model of clonal growth in the tall goldenrod, Solidago altissima. Our model was calibrated with field data on the clonal expansion of both seedlings and established clones, and model assumptions were verified by statistical analyses.When simulations were based on empirical distributions with long rhizome lengths, there was greater dispersal, less leaf overlap, and less spatial aggregation than when simulations were based on distributions with comparatively short rhizome lengths. For the field data that we utilized, variation in rhizome lengths had a greater effect than variation for either branching angles or rhizome initiation points (see text). We also found that observed patterns of clonal growth in S. altissima did not cause the formation of fairy rings. However, simulations with an artificial distribution of branching angles demonstrate that fairy rings can result solely from a plant's clonal morphology.Stochastic simulation models that incorporated variation in rhizome lengths, branching angles, and rhizome initiation points produced greater dispersal and less leaf overlap than deterministic models. Thus, variation for clonal growth parameters may increase the efficiency of substrate exploration by increasing the area covered and by decreasing the potential for intraclonal competition. We also demonstrated that ramet displacements were slightly, but consistently lower in stochastic simulation models than in random-walk models. This difference was due to the incorporation of details on rhizome bud initiation into stochastic simulation models, but not random-walk models. We discuss the advantages and disadvantages of deterministic, stochastic simulation, and random-walk models of clonal growth. 相似文献
123.
Continuous shoot growth monitoring in hydroponics 总被引:1,自引:0,他引:1
A weighing apparatus for automatic recording of fresh weight of shoots of spinach plants ( Spinacia oleracea L., cv. Subito) growing in nutrient solution is described. The system was tested for 17 days in a controlled environment and enabled the determination of the relative growth rate (RGR) of the shoot fresh weight. Results from three consecutive growth experiments demonstrated diurnal fluctuations in the relative growth rate of the shoot fresh weight. In general, relative growth rates were between 0.32 and 0.36 day−1 16 days after sowing and decreased to between 0.11 and 0.18 day−1 during the 12 following days. The variance between three replicate growth curves was compared with the variance of a growth function fitted through destructively obtained spinach shoot weight data. 相似文献
124.
Inhibition of auxin-induced elongation and xyloglucan breakdown in azuki bean epicotyl segments by fucose-binding lectins 总被引:3,自引:0,他引:3
Auxin-induced elongation of epicotyl segments of azuki bean ( Vigna angularis Ohwi and Ohashi cv. Takara) was suppressed by fucose-binding lectins from Tetragonolobus purpureus Moench and Ulex europaeus L. These lectins also inhibited auxin-induced cell wall loosening (decrease in the minimum stress-relaxation time of the cell walls) of segments. Auxin caused a decrease in molecular mass of xyloglucans extracted with 24% KOH from the cell walls. The lectins inhibited auxin-induced changes in molecular mass of the xyloglucans. The autolytic release of xylose-containing products from the pectinase-treated cell walls was also suppressed by the lectins. Fucose-binding lectins pretreated with fucose exhibited little or no inhibitory effect on auxin-induced elongation, cell wall loosning, or breakdown of xyloglucans. These results support the view that the breakdown of xyloglucans is involved in the cell wall loosening responsible for auxin-induced elongation in dicotyledons. 相似文献
125.
Developing pods of pea ( Pisum sativum L. cv. Alaska no 7) were used to study the enzymes of sucrose metabolism. Acid and neutral invertase (EC 3.2.1.26). sucrose synthase (SS, EC 2.4.1.13) and sucrose phosphate synthase (SPS, EC 2.4.1.14) have been localized in the soluble fraction. Acid invertase activity was also present in the insoluble fraction and in pea ovary apoplast. In pea pods, sucrose breakdown was dominated by the invertase pathway. SS specific activity only increased at late stages of parthenocarpic pod development, while SPS did so in pods obtained by pollination. Changes in time course of invertase activities have been correlated with the growth rate of fruits induced to develop either by fertilization or by exogenous application of giberellic acid (GA), 2,4-dichloro-phenoxy acetic acid (2,4-D) or 6-benzylaminopurine (6-BAP). The soluble neutral activities might be associated with pod elongation, while the acid ones were rather related to assimilate import by the induced fruits. Application of gibberellic acid to non-pollinated ovaries significantly enhanced the soluble neutral invertase activity before any ovary outgrowth was detected (up to 2 h after treatment). Within the same period of time. GA-treated ovaries showed a decrease in the acid invertase activity of the soluble fraction and an increase of the acid invertase activity in the apopiast. preceding in time the increment of the acid invertase activity associated with the insoluble fraction. Our results suggest that the early GA response may be mediated through a promotion of processes of protein secretion. 相似文献
126.
The morphological development and N uptake patterns of spring barley (Hordeum vulgare L.) genotypes of Northern European (Nordic) and Pacific Northwest US (PNW) origin were compared under two diurnally fluctuating root temperature regimes in solution culture. The two regimes, 15/5°C and 9/5°C day maximum/night minimum temperatures, simulated soil temperature differences between tilled vs. heavy-residue, no-till conditions, respectively, observed during early spring in eastern Washington. Previous field experiments indicated that some of the Nordic genotypes accumulated more N and dry matter than the PNW cultivars during early spring under no-till conditions. The objective of this experiment was to determined whether these differences 1) are dependent on the temperature of the rooting environment, and 2) are correlated with genotypic differences in NH4
+ and NO3
– uptake. Overall, shoot N and dry matter accumulation was reduced by 40% due to lower root temperatures during illumination. Leaf emergence was slowed by 14 to 22%, and tiller production was also inhibited. All genotypes absorbed more ammonium than nitrate from equimolar solutions, and the proportion of total N absorbed as NH4
+ was slightly higher in the 9/5°C than the 15/5°C regime. A Finnish genotype, HJA80201, accumulated significantly more shoot N than the PNW cultivars, Clark and Steptoe, and also more than a Swedish cultivar, Pernilla, in the 9/5°C regime. In the 15/5°C regime Steptoe did not differ in shoot N from the Nordic genotypes, while Clark remained significantly lower. These differences were not correlated to relative propensity for N form. Root lengths of the Nordic genotypes were significantly greater than the PNW genotypes grown under the 9/5°C regime, while the root lengths in the warmer root temperture regime were not significantly different among genotypes. Higher root elongation rates under low soil temperature conditions may be an inherent adaptive mechanism of the Nordic genotypes. Overall, the data indicate that lower maximum daytime temperatures of the soil surface layer likely account for a significant portion of the growth reductions and lower N uptake observed in no-till systems. 相似文献
127.
An inflatable minirhizotron system for root observations with improved soil/tube contact 总被引:3,自引:1,他引:2
Commonly used minirhizotrons consisting of a transparent tube inserted into the soil seldom attain good contact between the tube and the soil, which leads to root growth occurring in a gap rather than in the soil. A new system is described involving an inflatable flexible rubber wall, made from a modified motorcycle tube. Pressure ensures a proper tube/soil contact so that the environmental circumstances for root growth along the tube more closely correspond to those in the undisturbed soil. Before the endoscope slide is introduced into the minirhizotron for taking pictures, the inflatable tube is removed, so that there is no-often opaque-wall between the endoscope and the roots. This improves the picture quality and facilitates the analysis of root images. 相似文献
128.
Penetrometer resistance,root penetration resistance and root elongation rate in two sandy loam soils
Root penetration resistance and elongation of maize seedling roots were measured directly in undisturbed cores of two sandy
loam soils. Root elongation rate was negatively correlated with root penetration resistance, and was reduced to about 50 to
60% of that of unimpeded controls by a resistance of between 0.26 and 0.47 MPa. Resistance to a 30° semiangle, 1 mm diameter
penetrometer was between about 4.5 and 7.5 times greater than the measured root penetration resistance. However, resistance
to a 5° semiangle, 1 mm diameter probe was approximately the same as the resistnace to root penetration after subtracting
the frictional component of resistance. The diameter of roots grown in the undisturbed cores was greater than that of roots
grown in loose soil, probably as a direct result of the larger mechanical impedance in the cores. 相似文献
129.
An experiment to study the effects of Mg nutrition on root and shoot development of the Al-sensitive sorghum (Sorghum bicolor (L.) Moench) genotype CV323 grown in pots of sandy loam under different acid soil stress is reported. This experiment had
a factorial design: four rates of liming were combined with four rates of Mg fertilization. When no Mg was added, the pH of
the soil solutions (collected in ceramic cups) increased from 4.0 (unlimed) to 4.2, 4.7 and 5.9 at the increasing rates of
liming. After 30 days of growth dry matter yields of the limed treatments were 40%, 115% and 199% higher than that of the
unlimed treatment. Without liming and at the highest liming rate, adding Mg did not affect plant biomass significantly. At
the two intermediate levels of liming, however, 11.3 mg extra Mg per kg soil increased dry matter yield to the same levels
as found at the highest liming rate. Concentrations of Mg in the soil solution rose after Mg was added and fell when lime
was added, but adding both Mg and lime increased Mg concentrations in the plant shoots. In plants of the limed treatments,
dry matter yield was correlated closely with the Mg concentration in the shoot. This was not so in the unlimed treatment.
Furthermore, in the unlimed treatments root development was inhibited, but reduced Mg uptake by the plants resulted mainly
from the direct effect of Al- (or H-) ions in the soil solution rather than from impaired root development. It is concluded
that Mg fertilization counteracted the interfering effects of Al- and H ions on Mg uptake. 相似文献
130.
The growth of vegetative and reproductive shoots of Nicotiana tabacum L. cv. Xanthi is analyzed with the plastochron index to estimate the relationship between corolla growth and time. The plastochron of leaves 9 through 20 declines steadily at each successive node. The flower plastochron increases steadily during the growth of an individual cyme, with the most distal flower to open having the longest plastochron. Variation in the flower plastochron is the result of variation in the rate of flower initiation, not the growth rate of individual flowers. The corolla has an extended phase of approximately constant relative growth in length (between 0.2 · d–1 and 0.3 · d–1) until a peak of growth (0.5 · d–1) 2–3 d before anthesis. Corollas also have periodic peaks and troughs of growth that are low in amplitude (0.1 · d–1), but persist throughout most of corolla development. The pattern of corolla expansion contrasts strongly with earlier reports of the pattern of tobacco leaf growth.Abbreviations PI
plastochron index
- PR
plastochron ratio
- RGR
relative growth rate in length
The authors thank: Drs. T. Sage and E.G. Williams for the considerable time and space they invested; the members of Dr. R. Wyatt's laboratory for allowing us to use their computer facilities; A. Tull and M. Smith for their care taken in the green-house. This research was supported by U.S. Department of Agriculture grant GAM-89-01056 and by National Science Foundation grant DCB-87-15799. 相似文献