摘要:

Mulching plays an important role in ameliorating soil and environmental stresses of most tropical crops. But for non‐tropical crops such as potato, the beneficial effects are somewhat obscured by the incompatibility of mulching with existing soil and crop management practices. This paper reviews the main features of mulching. It basically describes the performance of selected mulch materials in potato systems, assesses their beneficial and/or adverse effects, and outlines potential avenues for developing efficient mulching techniques for potato.

ISSN:0190-4167    

DOI:10.1080/01904169509364926

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Growth response of soybean [Glycine max(L.) Merr. ‘Bragg'] grown in open top field chambers at five carbon dioxide (CO2) concentrations ranging from 349 to 946 μLL‐1and under two water regimes was examined. During reproductive growth, plants grown under CO2enrichment exhibited increases in total leaf area and dry weight. Water stress inhibited growth at all CO2levels, but the relative enhancement of growth due to CO2enrichment under water‐stressed (WS) conditions was greater than under well‐watered (WW) conditions. Water‐stressed plants grown under 946 μLL‐1CO2were larger than WW plants grown under 349 μLL‐1CO2. Reproductive yield increases were represented by increases in seed number rather than larger seeds. Although water stress reduced yield, the relative increase in seed number in response to elevated CO2was greater for WS plants. Leaf tissue analysis suggested that a phosphorus deficiency may have restricted the seed dry weight response to elevated CO2. The mean relative growth rate (RGR) and mean net assimilation rate (NAR) increased with CO2concentration in the first interval (5 to 14 days after planting) and diminished with time thereafter for each CO2level. At the second interval (14 to 63 days), the direct effect of NAR was offset by lower leaf area ratio (LAR). However, the LAR was greater for WS plants but the response of RGR to CO2was similar under both water treatments. At the third interval (63 to 98 days), the RGR for WS plants remained constant across CO2treatments, whereas under WW conditions a level response of NAR coupled with a negative response of LAR resulted in a decrease in RGR under CO2‐enriched conditions. The decrease in LAR was attributed to a decrease in specific leaf area. Leaf weight ratio was unaffected by CO2.

ISSN:0190-4167    

DOI:10.1080/01904169509364927

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Ozone toxicity can reduce soybean yields by an estimated 5 to 20%. The most economical and practical solution to the problem would be to use ozone‐tolerant cultivars. Because ozone toxicity is an oxidative stress, one would expect that plants having higher concentrations and proper kinds of antioxidants would be more tolerant. To test this hypothesis, 20 soybean lines or cultivars varying in contents of flavonol glycosides (naturally occurring antioxidants) were tested for ozone tolerance in a fumigation chamber and in phyto‐toxic concentrations of ozone in ambient, unfiltered, air in a greenhouse. In general, ozone tolerance was associated with the presence of kaempferol glycosides, particularly K3 through K6 and K9. Lines containing no kaempferol glycosides (OX942 & OX281) were among the most sensitive to ozone stress. The K9 compound has been associated with reduced numbers of stomata, drought tolerance, and slower growth rates, and this could reduce ozone absorption and toxicity, or K9 may be more effective in detoxifying ozone than other glycosides. Lee soybean was more tolerant to ozone and to manganese (Mn) toxicity (also an oxidative stress) than Forrest. Cross tolerances of plant genotypes to these two stresses deserve additional study. Among cultivars compared, Mukden was ozone tolerant, Columbia and Harosoy were sensitive, and Blackhawk was moderately sensitive.

ISSN:0190-4167    

DOI:10.1080/01904169509364928

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Ozone (O3) toxicity is a potential yield‐limiting factor for soybean (Glycine maxL. Merr.) in the United States and worldwide. The most economical solution to the problem is to use O3‐tolerant cultivars. Thirty‐four cultivars and 87 near‐isogenic lines (NILS) of soybean were screened for O3tolerance in a fumigation chamber (250 ppb for three hrs). Most tolerant cultivars tested were ‘Cloud’, ‘T‐276’, ‘T263’, and ‘Kindu’. Moderately tolerant cultivars included ‘Davis’, ‘T‐210’, and ‘Elton’. Most sensitive cultivars were ‘Corsoy 79’, ‘Noir’, and ‘Midwest’. The original ‘Clark’ cultivar was not tested, but ‘Clark 63’ tended to be more tolerant than ‘Harosoy’. The aluminum (Al)‐tolerant ‘Perry’ cultivar also tended toward greater O3tolerance than the Al‐sensitive ‘Chief’, as observed earlier. Our rankings of ‘Hark’ as moderately sensitive and ‘Davis’ as moderately tolerant are also in agreement with earlier reports. Among NILS, the order of O3tolerance was generally Williams>Clark>Harosoy, but differences were also observed within these parental groups. For example, L68–560 was more tolerant than some other NILS of ‘Harosoy’. ‘L76–1988’ appeared more tolerant to O3than other NILS of ‘Williams’, but all ‘Williams’ NILS were more tolerant than most NILS of ‘Harosoy’ and ‘Clark’. Ozone‐tolerant and ‐sensitive soybean cultivars or NILS identified in our study may be useful tools in studies on mechanisms of 03 tolerance and differential 03 tolerances in plants and in the development of ameliorative measures.

ISSN:0190-4167    

DOI:10.1080/01904169509364929

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effects of aluminum (Al) on photosynthesis and elemental uptake were studied in two wheat cultivars (Triticum aestivumL. cvs Yecora E, Nestos) differing in their tolerance to Al. Concentrations of calcium (Ca), magnesium (Mg), potassium (K), and iron (Fe) in the plant tissues of both cultivars grown in nutrient solutions (pH 4.5) decreased at all Al levels (0, 37.1, 74.1, and 148 μM). The tolerant cultivar Yecora E retained larger concentrations of all elements measured in roots and above ground parts compared with the non tolerant cultivar Nestos. Concentrations of Ca and Mg in leaves of the cultivar Nestos under high Al treatment were within the deficiency range. Changes in the shape of the chlorophyll fluorescence induction curves showed that Al‐stress altered thylakoid photofunctioning even in the more tolerant cultivar. Aluminum stress resulted in partial inhibition of photosynthetic electron transport at photosystem II and closure of photosystem II reaction centers. Chloroplast elemental loss and concomitant intrathylakoid acidification are postulated as mediating mechanisms for Al stress‐induced inhibition of photosynthesis.

ISSN:0190-4167    

DOI:10.1080/01904169509364930

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Cotton genotypes [Gossypium hirsutum(L.)] C‐310–73,‐307 (307) and C‐Sgl, 70–517 (517), shown previously to differ in tolerance to an acid (pH 5.1), high manganese (Mn) Grenada soil from Arkansas, were grown in nutrient solutions containing variable concentrations of excess Mn to confirm and characterize their postulated differences in Mn tolerance. Based on crinkle leaf symptoms and leaf dry weights, the 307 genotype was significantly more tolerant than 517 to 4, 8, or 16 mg Mn/L at a maintained pH of 4.6 (Experiment 1) and also to 4 or 8 mg Mn/L at an initial pH of 5.0, not subsequently adjusted (Experiment 2). In Experiment 1, the relative leaf dry weight (wt. with no Mn/wt. with 8 mg Mn/L × 100) was 94% for genotype 307 and only 27% for 517. In Experiment 2, the corresponding relative leaf weights were 75% and 26% for 307 and 517, respectively. Plant analytical results indicated that the 307 genotype tolerates a higher concentration of Mn in its leaves than does 517. This failure to correlate Mn tolerance with Mn concentrations in plant shoots agrees with previous findings when these two genotypes were grown in acid Grenada soil. Iron (Fe) concentrations, Fe/Mn ratios, and magnesium (Mg) concentrations were higher in the Mn‐tolerant 307 than in the Mn‐sensitive 517, but concentrations of phosphorus (P), potassium (K), calcium (Ca), copper (Cu), and zinc (Zn) were not related to Mn tolerance. Because differential Mn tolerance in these two genotypes is associated with differential internal tolerance to excess Mn, rather than differential Mn uptake, studies are needed to determine the chemical forms of Mn in tolerant and sensitive plants whose leaves contain comparable concentrations of total Mn. Because both Mn and Fe (closely related elements in the Mn toxicity syndrome) have spin resonances, electron paramagnetic resonance (EPR) offers promise in attacking the problem of differential Mn tolerance in plants.

ISSN:0190-4167    

DOI:10.1080/01904169509364931

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Nutrient availability can affect the onset of senescence. Phosphate‐phosphorus (P) was added at the recommended and five times the recommended level to a Bernow fine‐loamy, siliceous, thermic Glossic Paleudalf soil at Lane, OK. Senescence in stalk and shank internodes and cobs was rated in shrunken‐2 sweet corn (Zea maysL.) cultivars at various developmental stages. Plant dry weight was determined at fresh market harvest. Stalk internode senescence rating increased through harvest. The internode subtending the ear node was almost completely senescent at anthesis. There were statistical, but likely not biologically important, differences in stalk internode senescence between cultivars. Increased P occasionally increased stalk internode senescence rating and reduced plant dry weight. Increased P either decreased, or had no effect on, shank internode or cob senescence.

ISSN:0190-4167    

DOI:10.1080/01904169509364932

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Phosphorus (P) is a major nutrient factor influencing nitrogen (N) accumulation and partitioning of photosynthates in plants, especially the symbiotic N2‐fixation in legumes. This study was conducted to investigate how P application (0, 20, 40, and 60 kg P2O5/ha) affects symbiotic N2‐fixation of three cultivars (C 235, Pusa 408, and Pusa 417) of chickpea (Cicer arietinumL.). Application of P in general significantly increased leaf area, shoot dry weight, and the rate of acetylene (C2H2) reduction. Phosphorus concentration of shoots and roots, soluble sugar content of nodules, and shoot N accumulation were also significantly increased, especially by P at the 40 kg P2O5/ha rate. The P concentration in nodules was, however, not affected by different levels of P. The Pusa 417 cultivar responded better than the others to the P treatments. Phosphorus‐deficient plants accumulated sugar in their leaves. The interaction effect was found significant on leaf area, shoot dry weight, nodule number, and shoot N accumulation. Pusa 417 gave greatest response to 40 kg P2O5/ha but Pusa 408 and C 235 interacted best with the 20 kg P2O5/ha rate only. The increased nodulation and symbiotic N2‐fixation on P application seem to be the result of morphologically advanced shoots which are making more photosynthates for transport to nodules and not the direct effect of P on the nodules.

ISSN:0190-4167    

DOI:10.1080/01904169509364933

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Fertilizer application, particularly nitrogen (N), is important in cool‐season grass forage production. Subsurface (knife) placement of N often has resulted in higher forage yield and N uptake of tall fescue (Festuca arundinaceaSchreb.) compared to surface‐broadcast fertilization, but further studies were needed to indicate whether soil pH, phosphorus (P), or potassium (K) modifies the response. Experiment I tested responses of forage yield and N and P concentration to N, P, and K amount and placement. Two types of fertilizer placement ‐ broadcast and knife ‐ were used with 13, 112, or 168 kg N; 0 or 19 kg P; and 0 or 37 kg K/ha in a factorial arrangement. Yields increased by 53% as N fertilization went from 13 to 112 kg/ha and by 69% as N increased from 13 to 168 kg N/ha. Forage yield was increased 26% from knife compared to broadcast fertilizer placement. P application increased forage production by 13%, but K application had no effect on yield. Forage N concentrations increased by 25% as N fertilization went from 13 to 112 kg/ha and by 38% as N increased from 13 to 168 kg N/ha. Effects of added P and fertilizer placement on N concentration often resulted in interactions among factors. Forage P generally was increased by added P, with some effects of interactions among N rate, P rate, and placement. In Experiment II, fescue responses to N placement were tested where different soil characteristics had been established by previous lime and fertility treatments. Forage yield, N concentration, and N uptake were highest where 9.36 Mg/ha of lime were applied as compared to the control. Previous fertility treatments had no significant (P<0.05) effect. When N was knifed, forage yield was related positively to available soil P but not to pH or K. Yield and forage N concentration and uptake were increased by 20, 11, and 33%, respectively, as a result of knife versus broadcast N application.

ISSN:0190-4167    

DOI:10.1080/01904169509364934

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An understanding of nitrogen (N) interactions with plant growth and metabolism is important in order to increase the efficiency of fertilizer amendments for crop production. This study was initiated to evaluate the effect of the form of N and buffering with calcium carbonate (CaCO3) on the activity of ammonium (NH4) assimilating enzymes in a maize hybrid, a GDH‐deficient mutant, and the N6 normal inbred the mutant was derived from. Plants were grown in a growth chamber in sand culture with 10 mM of the different N forms [nitrate (NO3), NH4, ammonium nitrate (NH4STO3), and NH4plus CaCO3). Hybrid plants grown in the unbuffered NH4were much smaller than those grown in NO3as the only source of N, but had comparable growth with each source of nitrogen if the pH was controlled. In contrast, a glutamate dehydrogenase‐deficient mutant (GDH) inbred and its normal control grew almost as well on both NH4treatments as on NO3. GDH activity was higher in plants grown with NH4than NO3, and it was almost nil in tissue of the GDH deficient mutant. Glutamine synthetase (GS) activity was lower in the unbuffered NH4treatment (acid pH) and increased significantly when CaCO3was added to the NH4. Ammonium, as a sole source of N, induced a higher concentration of free ammonium and most free amino acids in plant tissues than NO3.

ISSN:0190-4167    

DOI:10.1080/01904169509364935

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor