Stoffbildung, CO2-Gaswechsel, Kohlenhydrat- und Stickstoffgehalt von Winterweizen bei erhöhter CO2-Konzentration und Trocken-streß

Dry Matter Production, CO₂ Exchange, Carbohydrate and Nitrogen Content of Winter Wheat at Elevated CO₂ Concentration and Drought Stress
Methods of mathematical modelling and simulation are being used to an increasing degree in estimating the effects of rising atmospheric CO₂ concentration and changing climatic conditions on agricultural ecosystems. In this context, detailed knowledge is required about the possible effects on crop growth and physiological processes. To this aim, the influence of an elevated CO₂ concentration and of drought stress on dry matter production, CO₂ exchange, and on carbohydrate and nitrogen content was studied in two winter wheat varieties from shooting to milk ripeness. Elevated CO₂ concentration leads to a compensation of drought stress and at optimal water supply to an increase of vegetative dry matter and of yield to the fourfold value. This effects were caused by enhanced growth of secondary tillers which were reduced in plants cultivated at atmospheric CO₂ concentration. Analogous effects in the development of ear organs were influenced additionally by competitive interactions between the developing organs. The content and the mass of ethanol soluble carbohydrates in leaves and stems were increased after the CO₂ treatment and exhausted more completely during the grain filling period after drought stress. Plants cultivated from shooting to milk ripeness at elevated CO₂ concentration showed a reduced response of net photosynthesis rate to increasing CO₂ concentration by comparison with untreated plants. The rate of dark respiration was increased in this plants.     

Effect of Elevated CO2 and Nitrogen Nutrition on Photosynthesis, Growth and Carbon-Nitrogen Balance in Brassica juncea

The response of Brassica juncea var. Bio-183-92 to elevated CO₂ under increased nitrogen treatment was studied. There was an interactive effect of CO₂ and nitrogen nutrition, indicating that, on the addition of more nitrogen, the plants sustained the positive effect of CO₂ enrichment by utilizing additional carbohydrates for the development of new sinks. Excess carbohydrate enables plants to be flexible and responsive to additional nitrogen application to sustain the CO₂ enrichment effect.     

Seasonal Changes in the Photosynthetic Capacity of Winter Rape Plants under Different Nitrogen Regimes Measured in the Field

Winter rape (cv.'Falcon') grown under different nitrogen regimes (N₀, N₁₂₀; 0 and 120 kg.ha⁻¹, respectively) in northern Germany was investigated over the 1996 spring–summer season. Using a CO₂, H₂O diffusion porometer, diurnal courses or net photosynthesis and respiration were measured in situ and were related to microclimatic conditions and leaf water relations. Photosynthesis was modelled and daily CO₂ gain was calculated. In contrast to the N₁₂₀ plants, plants of the low nitrogen plot (N₀) grew less densely and their leaves behaved more like sun leaves. Increased nitrogen supply had little influence on photosynthetic capacity but it increased productivity through higher leaf area index and an extended period of photosynthetic activity. N₁₂₀ plants also appeared to be better acclimated to hot, summer conditions. Higher nitrogen supply substantially increased seed production with the yield of the N₁₂₀ plants being 16% of the N₀ plants.     

Effects of the Application of Amorphous Silica on Transpiration and Photosynthesis of Soybean Plants Under Varied Soil and Relative Air Humidity Conditions

In epidermal cell walls of soybean leaves treated with amorphous silica accumulation of silica could be detected by means of electron microscopy and electron probe microanalysis. This changed the physical properties of the cell wall and affected the cuticular transpiration and uptake of CO₂: When the soil in which the plants were grown was dry (60% of the field capacity) and relative air humidity was below 50 %, the loss of water through the cuticle was smaller than the loss of CO₂ uptake. This caused a higher grain yield under the conditions of temporarily restricted low air humidity.     

Characterization of CO2 Responsiveness in a Brassica oxycamp Interspecific Hybrid

A study of the characterization of CO₂ responsiveness in Brassica oxycamp and its parents Brassica oxyrrhina and Brassica campestris was done using open top chamber technology. The response of the X. B. oxycamp (hybrid) to elevated CO₂ was significantly positive in respect of photosynthesis and growth and similar to that of its parent B. campestris. X B. oxycamp and B. campestris with greater sink potential responded significantly, whereas B. oxyrrhina with a poor sink, did not respond to CO₂ enrichment. Photosynthetic changes at elevated CO₃ levels in the hybrid and parents are partially attributed to the CO₂ effects on stomatal conductance and chlorophyll fluorescence.     

Seed Composition, Seedling Emergence and Early Seedling Vigour of Red Kidney Bean Seed Produced at Elevated Temperature and Carbon Dioxide

Understanding the influence of growth temperature and carbon dioxide (CO₂) on seed quality in terms of seed composition, subsequent seedling emergence and early seedling vigour is important under present and future climates. The objective of this study was to determine the combined effects of elevated temperature and CO₂ during seed-filling of parent plants on seed composition, subsequent seedling emergence and seedling vigour of red kidney bean ( Phaseolus vulgaris ). Plants of cultivar 'Montcalm', were grown at daytime maximum/nighttime minimum sinusoidal temperature regimes of 28/18 and 34/24 °C at ambient CO₂ (350 μmol mol⁻¹) and at elevated CO₂ (700 μmol mol⁻¹) from emergence to maturity. Seed size and seed composition at maturity and subsequent per cent emergence, early seedling vigour (rate of development) and seedling dry matter production were measured. Elevated CO₂ did not influence seed composition, emergence, or seedling vigour of seeds produced either at 28/18 or 34/24 °C. Seed produced at 34/24 °C had smaller seed size, decreased glucose concentration, but significantly increased concentrations of sucrose and raffinose compared to 28/18 °C. Elevated growth temperatures during seed production decreased the subsequent per cent emergence and seedling vigour of the seeds and seedling dry matter production of seed produced either at ambient or elevated CO₂.     

The Influence of Plant Water Stress on Net Photosynthesis and Leaf Area of Two Maize (Zea mays L.) Cultivars

The effect of plant water stress on net photosynthesis and leaf growth were investigated in order to determine to what extent leaf water potential during vegetative growth and silking affects maize development.
Two commercial maize hybrids grown in pots in a glasshouse were subjected to leaf water potentials of -1300 and -1700 kPa during the eighth leaf stage and during silking to -1700 and -2300 kPa to previously unstressed, moderately and severely stressed plants. The effect of stress on inhibiting CO₂ uptake rates and leaf areas, as well as the recovery after alleviating stress, were compared to that of unstressed plants.
No substantial differences in CO₂ uptake rates were found between medium and long seasoned cultivars. The CO₂ uptake rates per unit leaf area decreased to negative values under both moderate and severe stress conditions during both growth stages. During silking, the recovery of CO₂ uptake rate was much lower than during the eight leaf stage. Leaf area decreased proportionally with increased stress but did not recover after alleviating stress on plants stressed during both the eighth leaf and silking stages.     

Effect of Elevated CO2 on the Photosynthesis, Growth and Water Relation of Brassica Species Under Moisture Stress

An attempt has been made to study the interactive effect of elevated CO₂ and moisture stress on photosynthesis, growth and water relations of Brassica species using open top chambers. It was observed that plants responded to elevated CO₂ significantly under moisture stress condition mitigating the adverse effects on photosynthesis and growth of Brassica species. Relatively drought susceptible species, viz. B. campestris and B. nigra , responded to elevated CC₂ markedly as compared to less sensitive B. carinata and B. juncea plants. The water status of plants significantly improved under elevated CO₂ concentration possibly by increasing stomatal resistance and/or by increased root growth.     

Response of Mustard to Ethrel Spray and Basal and Foliar Application of Nitrogen

In a field trial conducted during 1992–93 and 1993–94, the effect of basal (B) nitrogen (N) (45 and 60 kg N ha⁻¹) and foliar application (F) of water (W) or 10 kg N ha⁻¹ and 400 or 600 ppm ethrel (E) (2-Chloro ethyl phosphonic acid) at 70 days after sowing was studied on leaf area index and dry mass at 90 days and pod number per plant, seeds per pod, 1000 seed weight, seed yield, oil content and oil vield at harvest of mustard ( Brassica juncea L. Czern & Coss.) cv. T-59. Recommended basal (B) application of 90 kg N ha (BN₉₀) was used as control. On the basis of 2 year data it was found that basal application of 60 kg N and foliar spray of 10 kg N ha ⁻¹ and 600 ppm ethrel gave higher values for growth and yield characteristics and enhanced seed yield and oil yield by 12.5 and 14.8%, respectively over control BN_90.     

Pflanzenwachstum durch CO2/HCO3-Eintrag über die Wurzel

Plant Growth after Application of CO₂/HCO₃ to the Roots
After applying H¹⁴CO₃ to the root system of summer wheat in hermetically sealed pots, absorption and incorporation of HCO₃ in the sugar-, starch-, and fibre-fraction (approximately 50 % of the absorped ¹⁴C) could be shown. This fraction reached 0.44–1.21 % of total C-assimilation of the shoot during growing stage F9/F10 on the Feeke-scala. 1/3 of the HCO₃-fraction resting in the soil was bound organically indicating that microorganisms may be able to utilize exogenous anorganic CO₂/HCO₃ for their photosynthesis.     

Effect of Gibberellic Acid Spray and Basal Nitrogen and Phosphorus on Productivity and Fatty Acid Composition of Rapeseed-Mustard

Two field experiments were conducted during] 994-95 to study the effect of spray of 10⁻⁵ M GA3 at 40 days after sowing on mustard ( Brassica juncea (L.) Czern & Coss.) cv. Varuna grown with basally applied 0, 40, 80 and 120 kg N ha⁻¹ (Expt. 1) and 0,15, 30 and 45 kg P ha⁻¹ (Expt. 2) on pod number per plant, seeds per pod, 1000 seed weight, seed yield, biological yield, harvest index and fatty acid composition of oil. No significant difference between water and GA3 spray was found when basally applied nitrogen was 0 or 40 kg N ha⁻¹. N₈₀ proved to be the best for yield characteristics. In another experiment on phosphorus, GA₃ and 30 kg P ha⁻¹ individually enhanced the yield, but interaction of GA₃ and P remained non-significant. The fatty acid composition of oil in both experiments was significantly affected only by nitrogen and phosphorus treatments for oleic acid and erucic acid. It was found that return in the form of yield was more for every kg applied fertilizer under GA, spray treatment. The response was more for N fertilizer in comparison to P. GA₃ at a low level of fertilization significantly increased the return from fertilization.     

Influence of Soil Drought on Plant Growth, Assimilation and Dissimilation of CO2 and Accumulation of Photosynthates in Field Bean (Vicia faba L. minor) During Pod Formation and Rapid Pod Growth

Field bean planes cultivar Nadwiślański were submitted to soil drought (30 % of field soil water capacity) for 5 days at the stage of pod formation (A) and of rapid pod growth (B) and then exposed for 20 minutes to ¹⁴CO₂. Radioactivity of leaves, stems, roots, and pods or pod shells and seeds was measured 1, 5, 24 and 48 hours after exposition.
In both stages soil drought reduced by about five times total CO₂ assimilation, mainly owing to lower activity of the photosynthetic apparatus and also, though less so, to reduced leaf growth. Photosynthetic activity referred to the dry weight of the leaves dropped to 22-35% of controls. Accumulation of photosynthetates in generative organs was much less depressed than ¹⁴CO₂ assimilation. 48 hours after exposition to ¹⁴CO₂ of drought treated plants, the contents of ¹⁴C of pods in phase A, and seeds in phase B, amounted to respectively 24% and 36% of assimilated ¹⁴C and equalled 91.5% and 74% of the corresponding values for controls.
The progressive decline of radioactivity in leaves and stems after ¹⁴CO₂ exposition was distinctly correlated to the rise of radioactivity of generative organs both in soil drought treated plants and in controls. Slightly lower values of correlation coefficients in drought treated plants may indicate impairment under drought conditions of synchronization in processes of unloading and accumulation of assimilates.
In plants drought treated in phase A the ability to dissimilate ¹⁴C was reduced to about 59% of that in controls, but when drought was applied in phase B, dissimilation rate was about three times as high.     

Irrigation Water Management for Efficient Water Use in Mulched Onion

Caused by the necessarily imperfect seed placement accuracy of sowing machines and, additionally, caused by many other biotic and abiotic factors, the resulting plant stands exhibit nonregular spatial distributions of its plants. Based on several simplifying assumptions, a stochastic approach is developed which allows an estimation of the effects of nonregular spatial patterns on yield per area. In this approach, two random variables are attached to each plant: single plant yield E and individual space A . The latter is estimated by the area of Thiessen polygons. Yield per area, calculated by the expectation of the ratio E/A , can be approximately expressed dependent on the means ( Ē and Ā ) and coefficients of variation ( v _E and v _A ) of E and A and their correlation ( r _EA ). In relation to the commonly used estimate Ē/Ā for yield per area, one obtains yield decreases if v _A / v _E  <  r _EA . This inequality, however, will be usually valid in the field of applications. The theoretical approaches and results were applied to three experimental data sets for drilled seeds of winter oilseed rape ( Brassica napus L.) (plant density: 60 plants m⁻², row distance: 10 cm). These data sets are characterized by different accuracies of longitudinal distributions within rows (58 %, 101 %, 150 %): yield depression increases with an increasing variability of plant distances within rows.     

The Influence of Plant Water Stress on Net Photosynthesis and Yield of Sunflower (Helianthus annuus L.)

The effect of plant water stress on net photosynthesis, leaf growth, yield and yield-related components were investigated in a single experiment in order to determine in which way water deficits affect sunflower yields.
Sunflower plants, grown under controlled temperature regimes, were stressed during budding, anthesis and seed filling by withholding water until the leaf water potential reached -1600 and -2000 kPa. Leaf area of unstressed plants significantly exceeded that of plants under severe stress during all growth stages investigated. The CO₂ uptake rate per unit leaf area as well as the total uptake rate per plant, significantly diminished with stress, while this effect drastically increased during the reproductive phase of the plant. Although this resulted in significantly smaller heads and kernels, it did not affect the number of seeds borne in the inflorescence. Severe stress during anthesis and seed filling resulted in more empty kernels. Moderate and severe stress during budding significantly lowered both grain and oil yields while plants that experienced moderate stress during anthesis and seed filling significantly outyielded those under severe stress.     

Relationship of Root and Shoot Characters in Parent, F1 and F2 Populations of Rice

The direct and indirect contributions of root characters — root length, roots/plant, fresh and dry root weight on grain yield/plant were worked out from a 7 × 7 diallel set of rice hybrids. The materials were grown in pots with four replications. Path analysis was done at genotypic level of correlation.
The grain yield/plant showed positive correlation with all the root characters in parent, F₁ and F₂ except with roots/plant in F₁ population. Fresh root weight demonstrated positive direct effect on grain yield/plant in all the three generations. Roots/plant had highly positive direct effect in F₂. Direct effects were negative in respect of root length and dry root weight in F₂ generation.     

Recovery of Faba Bean (Vicia faba L.) Plants as Affected by Glyphosate

Two field experiments were carried out during 1982/83 and 1983/84 seasons at Experimental Farm of National Research Centre at Shalakan, Kalubia Governorate, Egypt, to study the reversal effect of glyphosate induced phytotoxicity on growth and yield and its components of faba bean by the application of growth factors, i.e., growth regulators, amino acids and nutrient elements at different concentrations. A split plot design with four replications was used in both seasons. The obtained results indicated clearly that: Glyphosate at the two higher doses exhibited varying degrees of phytotoxic symptoms and reduced all the faba bean plant characters except the number of branches/plant. GA₃ alone or in a mixture with cytokinin reversed the phytotoxic effect of the glyphosate herbicide on decreasing the plant height. Cytokinin at 4/1000, phenylalanine and tryptophan at both levels, as well as GA₃ at 50 ppm, reversed the phytotoxic effect of the glyphosate herbicide on decreasing the dry weight/plant cytokinin at 4/1000, tryptophan at both concentrations, as well as, phenylalanine at 500 ppm, reversed the phytotoxic effect of the glyphosate herbicide on decreasing the number and dry weight of pods, seed yield per plant and per ha.     

Stability Analysis of Winter-rape (Brassica napus L.) by Using Plant Density and Mean Yield per Plant

The yield F per area can be expressed multiplicatively by using yield components. For the most simple case of including only two yield components one obtains: F = X₁− X₂ with X₁= number of plants per area (= plant density) and X₂= mean yield per plant.
For normal variables X₁ and X₂ the phenotypic yield stability of F, which has been measured quantitatively by the variance V(F) of F, can be explicitly expressed dependent on 1) the component means, 2) the component variances and 3) the correlation between the two components. V(F), therefore, depends on 5 parameters.
For many applications the use of the coefficient of variation v of F instead of the variance itself may be advantageous, v can be explicitly expressed dependent on 1) the coefficients of variation of the yield components and 2) the correlation between the components, v, therefore, depends on 3 parameters.
The different conditions leading to the same phenotypic yield stability can be investigated by using these explicit expressions for V(F) and v.
The main purpose of the present paper is the application of these theoretical models and results to the data of an extensive field trial with winter-rape, which has been performed for 5 years with 4 plant densities and 3 row distances.
For the lowest plant density (40 plants/m²) there results a very good agreement between the theoretically expected and the experimentally obtained values for the phenotypic stability of yield per area. But, for the higher plant densities this result don't hold true. Possible causes and explanations are discussed in detail.     

Cumulative Effects of Pre-sowing Seed Treatment and Foliar Application of Salts in Improving Biomass and Grain Yield of Soybean in Moderate Saline/alkaline Soil

Field trial studies were carried out to find out whether performance of soybean could be improved as a result of pre-sowing soaking treatment of seeds. Comparatively pre-sowing seed treatment with KNO₃, NaNO₃, NaCl, thiourea and di-Ammonium phosphate (DAP) resulted in better development of the root and shoot system than the control. As a result of pre sowing seed treatment, there was an increase in dry matter production by 44, 27 and 32 % over the control in KNO₃, NaNO₃ and DAP treatments respectively. Similarly increase in seed yield was noticed in NaNO₃ (45 %), KNO₃ (40 %) and DAP (50 %) pretreated plants. The number of existing nodules was reduced both in the control and treated plants due to pH (8.4) of the soil.
To investigate the cumulative effects of foliar spray on plants raised from pre-sowing seed treatment, salt solutions (NaCl, KNO₃, NaNO₃, thiourea, DAP) at optimal level were sprayed separately three times at three different stages of development. As a result of foliar spray moderate increase in growth in KNO₃ (20 %), thiourea (29 %) and DAP (25 %) treatment was observed over the control. Seed yield increased significantly (56–70 %) in all treatments except NaCl spray, due to increase in the number of pods (41–63 %) per plant. Foliar spray of nutrients increased protein yield without affecting the oil content. It is suggested that a considerable fertilizer economy may be effected by coupling pre-sowing seed treatment with foliar fertilization.     

Influence of Exogenous Glycine Betaine on Gas Exchange and Biomass Production in Sunflower (Helianthus annuus L.) under Water Limited Conditions

This study investigated whether the exogenous application of glycine betaine (GB) could alleviate the adverse effects of water deficit on sunflower. Two sunflower lines, Gulshan-98 and Suncross, were subjected to water deficit at the vegetative or the reproductive stages of plant growth. Three levels (0, 50 and 100 mmol l⁻¹) of GB were applied as a pre-sowing seed treatment or as a foliar spray at the time of initiation of water deficit at the vegetative or reproductive stages. Foliar application of GB at the time of initiation of water deficit treatments showed a marginal increase in shoot biomass in drought-stressed plants. Exogenously supplied GB as a foliar spray also showed a positive role in reducing the effects of water deficit on net CO₂ assimilation rate, transpiration rate and sub-stomatal CO₂ concentration in both sunflower lines. Pre-sowing seed treatment with GB had no effects on the above-mentioned physiological and growth attributes in both normally irrigated and drought-stressed plants. Taken together, foliar application of GB increased net CO₂ assimilation rate which in turn showed a slight increase in growth of water-stressed plants but this increase was not related to stomatal regulation.     

Effect of Some Growth Factors and Glyphosate Herbicide on Pigments and Protein in Faba Beans (Vicia faba L.)

Two field experiments were carried out during 1982/83 and 1983/84 seasons at Experimental Farm of National Research Centre at Shalakan, Kalubia Governorate, Egypt, to study the effects of supplemental growth factors on the reversal of glyphosate-induced inhibition in photosynthetic pigments and protein in faba beans. A split plot design with four replications was used in both seasons. Glyphosate at 0,312 and 468 g.a.i./ha as well as the untreated treatment, arranged at random in main plots while, the growth factors, i.e., growth regulators, amino acids and nutrient elements at different concentrations distributed randomly in the sub plots. The results could be summarized as follows:
1. Glyphosate decreased chlorophyll a, b and carotenoides content and the total pigments content in the leaves of faba bean plants, as well as, the protein content of seeds and protein yield per hectare.
2. The treatments of phenylalanine at 500 ppm, urea at 1 %, cytolinin at 4/1000 and tryptophan at 500 ppm, reversed the glyphosate-induced-phytotoxicity on decreasing the chlorophyll a, b content and total pigments content in faba bean leaves. The same treatments, as well as, zinc sulfate at 1 %, reversed the glyphosate-induced-phytotoxicity on decreasing the carotenoids content in faba bean leaves.
3. The treatment of G a ₃ at 100 ppm gave the highest percentage of crude protein in seeds, while the lowest value was obtained from cytokinin at 4/1000, in both seasons.
4. The treatments of cytokinin at 4/1000, phenylalanine at 500 ppm and tryptophan at both levels, reversed the glyphosate-induced-phytotoxicity on decreasing the protein yield per h.