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1.
Water deficit is perhaps the most severe threat to sustainable crop production in the conditions of changing climate. Researchers are striving hard to develop resistance against water deficit in crop plants to ensure food security for the coming generations. This study was conducted to establish the role of fulvic acid (FA) application in improving the performance of hybrid maize (Zea mays L.) under drought. Maize plants were grown under normal conditions till tasselling and were then subjected to drought by cessation of water followed by foliar application of FA (1.5 mg l?1). Drought stress disrupted the photosynthetic pigments and reduced the gas exchange leading to reduction in plant growth and productivity. Nonetheless, exogenous FA application substantially ameliorated the adversities of drought by sustaining the chlorophyll contents and gas exchange possibly by enhanced levels of antioxidant enzyme (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) activities and proline. These beneficial effects yielded in terms of plant growth and allometry, and grain yield. It is interesting to note that FA application also improved the crop performance under well‐watered conditions. Hence, FA may be applied to improve the crop performance under drought and well‐watered conditions.  相似文献   

2.
The effect of drought stress on the antioxidant system and membrane lipid peroxidation in flag leaves of a super‐hybrid rice variety (Liang‐You‐Pei‐Jiu, LYPJ) during the grain filling period was studied. During prophase of water deficit up to day 6 at relative soil water content (RSWC) 88 %, 81 %, 69 %, the superoxide dismutase (SOD) activity descended slightly, but the activities of peroxidase (POD) and catalase (CAT) ascended rapidly. The content of ascorbic acid (AsA) and glutathione (GSH) decreased. The production rate of superoxide radical (O2?), the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were maintained in a low level (0.3481 nmolO2? mg?1 protein min?1, 170.17 μmol g?1 FW, 1.467 nmol g?1 FW, at day 6, respectively). The total membrane lipids and index of unsaturated fatty acids (IUFA) did not change obviously. Thereafter (day 9, 12, with 52 %, 28 %, respectively RSWC), the activities of these enzymes declined significantly, while the content of AsA + GSH showed a reverse tendency. However, O2? production rate, the contents of H2O2 + MDA also increased rapidly. As a result, the total membrane lipids and IUFA dramatically decreased. The results indicated that the whole protect system was destructed seriously; any single protective component could not resist the damage caused by drought stress.  相似文献   

3.
A field trial conducted on the melon cultivar Huanghemi irrigated with saline water was carried out in Minqin County in the 2‐year period, 2007 and 2008. In three irrigation treatments, different saline water concentrations were applied, that is 0.8 g l?1 (Control C), 2 g l?1 (Treatment S1) and 5 g l?1 (Treatment S2), reproducing the natural groundwater concentration in the county. The electrical conductivity of the saline water was as follows: 1.00, 2.66 and 7.03 dS m?1, respectively. The aims of the study were (i) to monitor water consumption and water potential, (ii) assess, during the whole crop cycle, some growth parameters and their relations for estimating the morpho‐functional plant response irrigated with saline water and (iii) determine the ion concentration in different plant tissues to evaluate which mechanism the plant activates in the presence of high salt concentrations. Under salinity stress, the plants sustained the concentration of Ca, Mg and K, but at a level not sufficient to limit the Na adsorption. Therefore, the melon yield decreased and it was determined by a displacement of the ratio K/Na and by a lower (total potential MPa). Consequently with increasing salinity, a significant reduction was observed in: water consumption (ET c, mm), leaf area duration (LAD, m2 d), on shoot dry weight aboveground (W , g plant?1), on specific leaf area (SLA, cm2 g?1) and on leaf area ratio (LAR, cm2 g?1). In treatment S2, in addition to these changes which mainly affected the plant morphology with effects on the biomass produced, a moderate reduction was also observed in net assimilation rate (NAR, g m?2 d?1), water use efficiency (WUE), a significant reduction in the energy conversion efficiency (ECE, %) and, in short, in a reduction in the relative growth rate (RGR, g g?1 d?1).  相似文献   

4.
The effects of culture media, explants and genotypes on shoot regeneration in oilseed Brassica species were examined in this study. The maximum shoot regeneration frequency was obtained in Murashige and Skoog medium supplemented with 3 mg l?1 6‐benzylaminopurine and 0.15 mg l?1 1‐naphthaleneacetic acid. The addition of 2.5 mg l?1 AgNO3 was very beneficial to shoot regeneration in B. napus and Ag2S2O3 (10 mg l?1) was even superior to AgNO3 (2.5 mg l?1). Explant age, explant type and carbon source also significantly affected shoot regeneration. Four‐day‐old seedlings of cotyledonary explants showed the maximum shoot regeneration frequency and number of shoots per explant. Of the four explants – peduncles, hypocotyls, cotyledons and leaf petioles – cotyledons produced the highest shoot regeneration frequency (56.67 %). Four carbon sources – glucose, maltose, starch and sucrose – were compared for their respective effects on shoot regeneration from cotyledonary explants. Sucrose appeared to be the best carbon source for shoot regeneration with the highest shoot regeneration frequency (76.00 %). Considerable variation in shoot regeneration from cotyledonary explants was observed both between and within Brassica species. The shoot regeneration frequency ranged from 10.00 % for cv. R5 (B. rapa) to 83.61 % for cv. N1 (B. napus). Two B. napus, one B. carinata and one B. juncea cultivars exhibited shoot regeneration frequency higher than 70 %. In terms of the number of shoots produced per explant, B. rapa showed the highest variation, ranging from 5.64 for cv. R3 to 1.33 for cv. R5. Normal plantlets were regenerated from all induced shoots and developed normally. The regenerated plants were fertile and identical with the source plants.  相似文献   

5.
The optimum temperature for maize germination is between 25 and 28 °C. Poor and erratic germination at suboptimal temperature is the most important hindrance in its early sowing. This study was conducted to induce chilling tolerance in hybrid maize (Zea mays L.) by seed priming with salicylic acid (SA) and to unravel the background biochemical basis. For seed priming, maize hybrid (Hycorn 8288) seeds were soaked in 50, 100 and 150 ppm (mg l?1) aerated solutions of SA for 24 h and were dried back. Treated and untreated seeds were sown at 27 °C (optimal temperature) and at 15 °C (chilling stress) under controlled conditions. Performance of maize seedlings was hampered under chilling stress. But seed priming with SA improved the seedling emergence, root and shoot length, seedling fresh and dry weights, and leaf and root score considerably compared with control both at optimal and chilling temperatures. However, priming in 50 mg l?1 SA solution was more effective, followed by priming in 100 mg l?1 SA solution. Seed priming with SA improved the chilling tolerance in hybrid maize mainly by the activation of antioxidants (including catalase, superoxide dismutase and ascorbate peroxidase). Moreover, maintenance of high tissue water contents and reduced membrane permeability also contributed towards chilling tolerance.  相似文献   

6.
The salt‐sensitive Glycine max N23674 cultivar, the salt‐born Glycine soja BB52 population, and their hybrid 4076 strain (F5) selected for salt tolerance generation by generation were used as the experimental materials in this study. First, the effects of NaCl stress on seed germination, tissue damage, and time‐course ionic absorption and transportation were compared. When qualitatively compared with seed germination appearance in culture dishes, and tissue damages on roots or leaves of seedlings, or quantitatively compared with the relative salt injury rate, the inhibition on N23674 was all the most remarkable. After the exposure of 140 mm NaCl for 1 h, 4 h, 8 h, 12 h, 2 days and 4 days, the content of Cl? gradually increased in the roots and leaves of seedlings of BB52, 4076 and 23674. Interestingly, the extents of the Cl? rise in roots of the three experimental soybean materials were BB52 > 4076 > N23674, whereas those in leaves were just on the contrary. Secondly, by using the scanning ion‐selective electrode technique (SIET), fluxes of Na+ and Cl? in roots and protoplasts isolated from roots and leaves were also investigated among the three experimental soybean materials. After 140 mm NaCl stress for 2, 4 and 6 days, and when compared with N23674, slighter net Cl? influxes were observed in root tissue and protoplasts of roots and leaves of BB52 and 4076 seedlings, especially at the cellular protoplast level. The results indicate that with regard to the ionic effect of NaCl stress, Cl? was the main determinant salt ion for salt tolerance in G. soja, G. max and their hybrid, and the difference in their Cl?/salt tolerance is mainly attributed to the capacity of Cl? restriction to the plant above‐ground parts such as leaves.  相似文献   

7.
Worldwide rice productivity is being threatened by increased endeavours of drought stress. Among the visible symptoms of drought stress, hampered water relations and disrupted cellular membrane functions are the most important. Exogenous use of polyamines (PAs), salicylic acid (SA), brassinosteroids (BRs), glycinebetaine (GB) and nitrous oxide (NO) can induce abiotic stresses tolerance in many crops. In this time course study, we appraised the comparative role of all these substances to improve the drought tolerance in rice (Oryza sativa L.) cultivar Super‐Basmati. Plants were subjected to drought stress at four leaf stage (4 weeks after emergence) by maintaining soil moisture at 50 % of field capacity. Pre‐optimized concentrations of GB (150 mg l?1), SA (100 mg l?1), NO (100 μmol l?1 sodium nitroprusside as NO donor), BR (0.01 μm 24‐epibrassinolide) and spermine (Spm; 10 μm ) were foliar sprayed at five‐leaf stage (5 weeks after emergence). There were two controls both receiving no foliar spray, viz. well watered (CK1) and drought stressed (CK2). There was substantial reduction in allometric response of rice, gas exchange and water relation attributes by drought stress. While drought stress enhanced the H2O2, malondialdehyde (MDA) and relative membrane permeability, foliar spray of all the chemicals improved growth possibly because of the improved carbon assimilation, enhanced synthesis of metabolites and maintenance of tissue water status. Simultaneous reduction in H2O2 and MDA production was also noted in the plants treated with these substances. Drought tolerance was sturdily associated with the greater tissue water potential, increased synthesis of metabolites and enhanced capacity of antioxidant system. Of all the chemicals, foliar spray with Spm was the most effective followed by BR.  相似文献   

8.
The newly identified smoke‐compound butenolide (3‐methyl‐2H‐furo[2,3‐c]pyran‐2‐one) can improve seedling vigour. This study highlights the effects of smoke‐water and butenolide on shoot and root elongation of a local rice variety. Smoke‐water (1 : 500) and butenolide (10?8 m ) treatments significantly increased shoot length. A low concentration of butenolide (10?10 m ) promoted maximum root length and seedling weight, which were significantly different from the control. Butenolide‐treated (10?8 m ) seedlings had a significantly greater number of lateral roots than untreated seedlings. The vigour index of smoke‐water (1 : 500) and butenolide‐treated (10?8 m ) rice seeds was significantly higher than that of untreated seeds. These findings suggest the possible use of butenolide for promoting vigorous seedlings in rice.  相似文献   

9.
This study investigates the effect of added silicon (Si, as sodium silicate) on water status–related parameters, osmolytes accumulation and gas exchange in the leaves of hydroponically grown upland rice seedlings under polyethylene glycol (PEG‐6000)‐induced water stress, the aims being to explore whether Si has been involved in osmotic adjustment (OA) in upland rice plants. Fifty‐five‐day‐old seedlings were subjected to 8.5 % (m/v) PEG‐6000 treatment without or with 2.5 mm Si for 7 days. The results showed that addition of Si to culture solution could partially improve total, free, and bound water contents in both leaves and roots, which were all decreased under water stress. Application of Si increased water potential (Ψw) and osmotic potential (Ψπ) in both roots and leaves while maintained higher turgor pressure (Ψp), in comparison with the plants without Si application. Added Si also stimulated the active accumulation of some osmolytes in both leaves and roots of stressed plants, which suggested enhanced OA ability. Analysis of gas exchange in leaves showed that net photosynthetic rate, transpiration, and water‐use efficiency (WUE) were decreased under water stress, whereas application of Si enhanced the photosynthesis and improved the WUE. This study suggests that PEG‐induced water stress in rice could be partially alleviated by addition of Si. This alleviative effect was partially attributable to enhanced OA ability by means of active accumulation of osmolytes.  相似文献   

10.
Despite exhaustive literature describing drought stress effects on photosynthesis in Gossypium hirsutum, the sensitivity of photosynthetic electron flow to water deficit is heavily debated. To address this, G. hirsutum plants were grown at a field site near Camilla, GA under contrasting irrigation regimes, and pre‐dawn water potential (ΨPD), stomatal conductance (gs), net photosynthesis (PN), actual quantum yield of photosystem II (ΦPSII) and electron transport rate (ETR) were measured at multiple times during the 2012 growing season. ΨPD values ranged from ?0.3 to ?1.1 MPa. Stomatal conductance exhibited a strong (r2 = 0.697), sigmoidal response to ΨPD, where gs was ≤0.1 mol m?2 s?1 at ΨPD values ≤ ?0.86 MPa. Neither ΦPSII (r2 = 0.015) nor ETR (r2 = 0.010) was affected by ΨPD, despite exceptionally low ΨPD values (?1.1 MPa) causing a 71.7 % decline in PN relative to values predicted for well‐watered G. hirsutum leaves at ΨPD = ?0.3 MPa. Further, PN was strongly influenced by gs, whereas ETR and ΦPSII were not. We conclude that photosynthetic electron flow through photosystem II is insensitive to water deficit in field‐grown G. hirsutum.  相似文献   

11.
Silicon (Si) can increase plant defence systems against abiotic and biotic stress, but there is little information on UV‐B radiation stress alleviation by Si for field crops. Using soybean (Glycine max (L.) Mell) seedlings, we determined how Si may mediate UV‐B radiation stress by studying changes in biomass, physiological attributes and antioxidants’ activities. The seedlings were raised with 0, 1.70 and 2.55 mm of Si in the growth chamber under ambient, ambient +2.7 kJ m?2 day and ambient +5.4 kJ m?2 day of UV‐B radiation. As expected, plants suffered severe growth limitations under UV‐B radiation, but Si alleviated these limitations through improvements in leaf area (LA) and root‐to‐shoot ratio (R/S). The UV‐B radiation stress reduced the LA by 73.9–94.7%, total dry weight (TDW) by 11.8–36.6% and R/S by 9.2–30.2% but induced the activities of soluble protein by 18.4–21.0%, catalase (CAT) by 22.7–54.2%, superoxide dismutase (SOD) by 31.9–63.1%, and peroxidases (POD) by as much as 162.9–381.6%. Further confirmation of stress alleviations by Si was noted from reductions in these stress signals (antioxidant activities) under UV‐B radiation: CAT decreased significantly by 78.3–79.4%, SOD by 5.3–7.2% and POD by 49.9–61.9% in silicon‐treated UV‐B stressed soybean.  相似文献   

12.
Crosses were made to produce interspecific hybrids between Brassica napus × B. juncea and their reciprocals with the aid of embryo culture techniques. A better response of hybrid embryo culture was obtained from two cross combinations of B. juncea × B. napus (Ames 24521 × Huyou 15 and Vittasso × Zheshuang 72) than from their reciprocals. Embryo culture was more effective in terms of plant regeneration when embryos were cultured in vitro at 15 days after pollination (DAP), while more calli were initiated when embryos were excised and cultured at 10 DAP. A better response was observed on the MS medium with 0.3 mg l?1 naphthylacetic acid (NAA) + 1.5 mg l?1 6‐benzylaminopurine (BAP) and with 0.3 mg l?1 NAA + 2.0 mg l?1 BAP. Callus formation and plant regeneration on these two media reached 55.43 and 26.65 %, and 66.98 and 24.61 %, respectively.  相似文献   

13.
Photosynthetic Response of Wheat to Soil Water Deficits in the Tropics   总被引：1，自引：0，他引：1  
The changes in photosynthetic rate and translocation of photosynthates in winter wheat (Triticum Aestivum L.) grown in lysimeters were studied, in response to periodic soil water deficit during late tillering and flowering stages. Soil water deficits were imposed to previously nonstressed plants during late tillering and flowering states. Timing of irrigation was scheduled according to the ratio between irrigation water applied and cumulative pan evaporation (IW/CPE) of 0.75 (low deficit), and 0.5 (moderate deficit), as well as by suspending irrigations after crown root initiation stage (severe deficit). To determine the rate of photosynthesis, a short radioactive pulse of 14CO2 with 300 ppm concentration was given to second leaf from the top at tillering, and to the flag leaf at flowering stages for 20 second exposure time. The translocation of photosynthates was estimated by scanning 14C activity in different plant parts. In late tillering the midday Photosynthetic rate (PR) was significantly 3 mg CO2 dm?2 h?1 lower under low water deficit (WD1) than under zero water deficit (WD0). Under higher stress conditions, soil water acted as a limiting factor to keep the rate from rising above 13.2 during stress at late tillering (WD2), 14.5 flowering (WD4), and 10.0 mg CO2 dm?2 h?1 for stress at both the growth stages (WD5), respectively. The difference in daily accumulated photosynthesis (8 h), between stressed and nonstressed were 15, 40, 42, and 77 mg CO2 dm?2 h?1 respectively at WD1 WD2, WD4, and WD5. The retention of 14C in flag leaf decreased considerably after 24 hours of exposure time when the labelled assimilates were translocated in bulk to the ear head. Under stressed condition a general trend was observed for upward translocation of assimilates towards the ear, even from the stem and root. The percent 14C activity observed in ear after 24 hours was greatest in severely stressed plants. The photosynthetic rate is reasonable predicted by midday LDR and surface moisture.  相似文献   

14.
Temporal and seasonal water deficit is one of the major factors limiting crop yield on the Canadian prairie. Selection for low carbon isotope discrimination (Δ13C) or high water‐use efficiency (WUE) can lead to improved yield in some environments. To understand better the physiology and WUE of barley under drought conditions on the Canadian prairie, 12 barley (Hordeum vulgare L.) genotypes with contrasting levels of leaf Δ13C were investigated for performance stability across locations and years in Alberta, Canada. Four of those genotypes (‘CDC Cowboy’, ‘Niobe’, ‘170011’ and ‘Kasota’) were also grown in the greenhouse under well‐watered and water‐deficit conditions to examine genotypic variations in leaf Δ13C, WUE, gas exchange parameters and specific leaf area (SLA). The water‐deficit treatment was imposed at the jointing stage for 10 days followed by re‐watering to pre‐deficit level. Genotypic ranking in leaf Δ13C was highly consistent, with ‘170011’, ‘CDC Cowboy’ and ‘W89001002003’ being the lowest and ‘Kasota’‘160049’ and ‘H93174006’ being the highest leaf Δ13C. Under field and greenhouse (well‐watered) conditions, leaf Δ13C was significantly correlated with stomatal conductance (gs). Water deficit significantly increased WUE, with ‘CDC Cowboy’– a low leaf Δ13C genotype with significantly higher WUE and lower percentage decline in assimilation rate (A) and gs than the other three genotypes (‘Niobe’, ‘170011’ and ‘Kasota’). We conclude that leaf Δ13C is a stable trait in the genotypes evaluated. Low leaf Δ13C of ‘CDC Cowboy’ was achieved by maintaining a high A and a low gs, with comparable biomass and grain yield to genotypes showing a high gs under field conditions; hence, selection for a low leaf Δ13C genotype such as ‘CDC Cowboy’ maybe important for maintaining productivity and yield stability under water‐limited conditions on the Canadian prairie.  相似文献   

15.
The molecular mechanism to control the oxidative burst exerted by Mn accumulation in rice (Oryza sativa L.) plants, grown in hydroponics containing 0.5, 2 and 8 mg l–1 Mn and irradiated with a total biological effective UV‐B irradiation of 20.825 kJ m?2, was investigated in the chloroplasts at the 15th and 21st days after germination. In both experimental periods, Mn accumulation kinetics in the leaves and in the chloroplast lamellae displayed overall increases. Coupled to higher membrane selectivity, superoxide production and acyl lipids peroxidation in the thylakoids decreased, prompting upper rates of the Hill and Mehler reactions. Connected to UV‐B irradiation, higher accumulated Mn in thylakoids was found to be chelated in a 36.5 kDa protein, with Mn/protein ratio of about 1 and high content of Gln, Asp, Glu, Leu and Gly, being its EPR spectrum characteristic of high‐spin Mn(II), in a S = 5/2 ground state. As this protein exhibited enzymatic catalysis of superoxide dismutation, it was concluded that, under UV‐B irradiation, the high internal tolerance of Oryza sativa L. to Mn during the vegetative growth also triggers the synthesis of a manganese protein that mimics superoxide dismutase functioning, therefore furnishing an additional intimate protection against oxidative stress.  相似文献   

16.
Abstract The objective was to study soil water conservation and physiological growth of wheat (Triticum aestivum L.) using composted cattle manure applied either as mulch or incorporated with soil at 20 Mg ha?1. Haruhikari, a relatively drought‐sensitive and Hongmangmai, a relatively drought‐tolerant wheat, were the cultivars studied under both adequate and deficit irrigation. Fourteen weeks after sowing (WAS), the number of tillers and leaves was significantly reduced by 19 % and 30 % respectively under deficit irrigation and Hongmangmai produced slightly (10 %) more tillers than Haruhikari. Unlike mulching, the incorporation of manure had favourable effects on plants in terms of shoot dry mass (SDM) by 36 % and number of tillers and leaves by 40 %. Haruhikari produced substantially (29 %) greater root mass under adequate irrigation but Hongmangmai produced slightly (2.7 %) more roots and responded much better to manure use whether under adequate or deficit irrigation. As a result, Hongmangmai suffered less severe reductions in tillers and biomass under water stress. In comparison, the mulched manure treatment saved 15 % and 64 % respectively more water than the control and the treatment incorporating manure, but this advantage in water‐saving did not translate to superior plant growth. Leaf water potential (ψl) under adequate irrigation significantly exceeded that under deficit irrigation by 27 % and the ψl of Haruhikari exceeded that of Hongmangmai by 15 %. However, Hongmangmai may be considered more tolerant of dehydration since it maintained much higher net photosynthetic rates (PN) even with a lower leaf water potential. The reduction in the PN and intracellular carbon dioxide concentration (Ci) of the cultivars under deficit irrigation was on account of decreasing stomatal conductance (gs) and transpiration rate but on average, the gs of Hongmangmai significantly exceeded that of Haruhikari by as much as 0.53 under adequate irrigation and 0.22 under deficit irrigation. In conclusion, we suggest that the drought tolerance of Hongmangmai was related to its superior root growth and greater ability than Haruhikari, to efficiently utilize incorporated manure for growth under water stress.  相似文献   

17.
This investigation tested the influence of thermal treatment of seeds at various stages of imbibition on the germination percentage, speed and growth response of seeds and seedlings. Seeds of sorghum (Sorghum bicolor L Moench) were treated in 2, 4 or 6 g NaCl l?1 solutions and exposed for 2 h to 45 °C during the first, second or third days of imbibition. Thereafter, the seeds were dried and germinated at 42/19 °C (day/night temperature). Salt treatments did not improve the final germination percentage but increased germination speed over untreated seeds. The higher the salt concentration used, the greater the dry weights of plumules and radicles. Thermal treatment on the third day of imbibition yielded higher germination percentages than untreated seeds, while thermal treatment on the second day gave faster germination. Both the second and third day thermal treatments gave superior germination indices and higher plumule‐to‐radicle ratios. It is concluded that thermal treatment may assist in acclimating seeds to heat stress.  相似文献   

18.
The cup plant (Silphium perfoliatum L.) is discussed as an alternative energy crop for biogas production in Germany due to its ecological benefits over continuously grown maize. Moreover, a certain drought tolerance is assumed because of its intensive root growth and the dew water collection by the leaf cups, formed by fused leaf pairs. Therefore, the aim of this study was to estimate evapotranspiration (ET ), water‐use efficiency (WUE ) and the relevance of the leaf cups for the cup plant's water balance in a 2‐year field experiment. Parallel investigations were conducted for the two reference crops maize (high WUE ) and lucerne‐grass (deep and intensive rooting) under rainfed and irrigated conditions. Root system performance was assessed by measuring water depletion at various soil depths. Transpiration‐use efficiency (TUE ) was estimated using a model approach. Averaged over the 2 years, drought‐related above‐ground dry matter reduction was higher for the cup plant (33 %) than for the maize (18 %) and lucerne‐grass (14 %). The WUE of the cup plant (33 kg ha?1 mm?1) was significantly lower than for maize (50 kg ha?1 mm?1). The cup plant had a lower water uptake capacity than lucerne‐grass. Cup plant dry matter yields as high as those of maize will only be attainable at sites that are well supplied with water, be it through a large soil water reserve, groundwater connection, high rainfall or supplemental irrigation.  相似文献   

19.
Leaching of nitrogen from permanent grassland treated with cattle slurry The objective of this study was to determine the effect of cattle slurry and mineral nitrogen fertilization on nitrate contamination of the interflow soil water. Field experiments were conducted at grassland research station ‘Rengen’ in the Eifel area (475 m a.s.L., 7.5 °C mean temperature, 806 mm mean yearly precipitation). In the respective plots soil consisted of 40 cm loamy material over a compact, almost water impermeable soil layer. The 2 × 6 m sized individual plots were prepared 1985 in a way so that surrounding soil was removed down to the compact soil layer about 45 cm deep and the monolith beeing packed by polyethylene sheets, waterproofing the plots down to the water impermeable soil layer. At the open lower ends of the plots near the soil surface and at 45 cm depth respectively, metal sheets were inserted to drain the surface run-off and interflow water into gutters and from there into collecting tanks. Nitrogen fertilization included two cattle slurry treatments (240 kg and 480 kg ha?1 a?1 total nitrogen), combination of mineral nitrogen with cattle slurry (200 kg + 160 kg ha?1 a?1) and mineral nitrogen treatments without slurry (200 kg - ha?1 a?1). Control plots received neither mineral nor slurry nitrogen. The quantification of interflow water and its nitrogen concentration started in 1986. In this year relatively high nitrate concentrations up to 56 mg l?1 appeared in the interflow water. 1987 nitrogen concentrations dramatically decreased to mean values between 10 and 15 mg l?1 in all fertilization treatments. Similar levels of nitrate concentrations were observed in the following two years. Total amounts of nitrogen losses did nor exceed 5 kg ha?1 a?1 in any of the years from 1986 to 1988, nor were differences observed in nitrate concentration among the fertilization treatments.  相似文献   

20.
Five cowpea genotypes, Gorom local (Go), KVX61‐1 (KV), Mouride (Mo), Bambey 21 (B21) and TN88‐63 (TN), differing in their susceptibility to water stress, were studied under glasshouse and field conditions, to determine their physiological, biochemical and agronomic responses to water deficit at flowering stage. Effect of water deficit on leaf water potential (ψl), canopy temperature, gaseous exchange, leaf proline content, total protein and starch contents, maximal quantum yield (ϕp0) and yield components was examined. Water deficit significantly increased the canopy temperature and the proline content of the five genotypes while ψl, gaseous exchanges, ϕp0 and starch content decreased significantly. Yield components, with the exception of seed number per pod, of the five genotypes, were also significantly affected. Under glasshouse and field conditions, the results showed that stomatal closure is the common strategy used by the five genotypes to avoid dehydration. Go, Mo and TN tolerated water stress better than B21 and KV. Furthermore, Go and Mo recovered more rapidly after rewatering than B21 and KV. These latter genotypes are revealed to be sensitive with low recovery capacity. The results suggest that the maintenance of net photosynthesis and solute accumulation seem to be traits conferring water stress tolerance in Go, Mo and TN. These traits and recovery capacity could be valuable selection criteria for higher yields under water deficit conditions.  相似文献   

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