摘要:

High metal availability, arising from mining and industrial activities, disposal of sewage sludge or soil acidification, is an increasing problem in agriculture and forestry. Metal toxicity causes multiple direct and indirect effects in plants which concern practically all physiological functions. In this review we consider the effects of excess heavy metals and aluminium on those functions which will alter plant water relations. After a brief comment on the metal effects in cell walls and plasmalemma, and their consequences for cell expansion growth, the influences of high metal availability on the factors which regulate water entry and water exit in plants are considered. Emphasis is placed on the importance of distinguishing between low water availability in mine and serpentine soils and toxicity effects in plants which may impair the regulation of a plant's water household. Examples on water relations of both plants grown on metalliferous soil and hydroponics are discussed. The effects of metal toxicity on root growth, water transport and transpiration are considered. It is concluded that future research has to focus on the mechanisms of metal‐induced inhibition of both root elongation and morphogenetic processes within roots. In order to understand the relation between metal tolerance and drought resistance better, further studies into metal tolerance mechanisms at the cell wall, membrane and vacuolar level, as well as into the mechanisms of drought resistance of plants adapted to metalliferous soils are required.

ISSN:0190-4167    

DOI:10.1080/01904169009364057

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Activity of the enzyme nitrate reductase was shown to increase in young leaves of tomato until the leaves reached full expansion, and then it declined. The increase in activity was shown to be due both to an increase in enzyme activity per gram fresh weight and an increase in leaf weight, and the decline in activity was due to a decrease in activity per gram. Nitrate reductase is a key enzyme for the assimilation of nitrate by plants, and the decline in its activity in the older leaves was shown to be more than compensated for by the growth of new leaves. There was an exponential increase in the total activity of the enzyme in the whole leaf system during vegetative growth, when the leaf system itself was increasing in weight exponentially.

ISSN:0190-4167    

DOI:10.1080/01904169009364058

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Although lupins (Lupinus angustifoliusL.) are usually grown in slightly acidic soils covering the pH range 6.0 to 6.5, the response of lupin cultivars to a range of acid soil infertility factors has not been investigated. Effects of external Ca concentrations of 150 or 1000 μM and S activities of monomeric Al species (Al reactive with aluminon in 30 min, without acidification and heating; SaA1mono) up to 80 μM on early growth and mineral composition in tops of three lupin cultivars (Unicrop, Uniharvest, and Uniwhite) were investigated in continuously flowing nutrient solution at pH 4.3 ± 0.1. The dry weight of tops of the three cultivars was generally similar in Uniwhite and Unicrop, and considerably lover in Uniharvest. The weight of tops increased by 24 to 39% while that of roots increased by 11 to 14% with an increase in Ca concentration from 150 to 1000 μM in Al‐free solutions. At each Ca concentration, an increase in activity of monomeric Al resulted in a linear decrease in dry weight of tops (r2= 0.516 to 0.961). The effect of Al on root weight vas significant only in Uniwhite at both Ca concentrations and in Uniharvest at 150 μM Ca.

ISSN:0190-4167    

DOI:10.1080/01904169009364059

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The evolutionary origin center of alfalfa within the extensive subhumid Transcaucasia has been a valuable source ofMedicagospp. for development of improved alfalfa cultivars. Centuries of natural outcrossing within the perennial, allogamousMedicagospecies complex resulted in numerous polymorphic plants with desirable genetic characteristics adaptive to harsh climatic and soil environs. Characteristic large coralioid noduiation ofM.media(M.falcataXM.sativa) provides means for improved symbiotic nitrogen fixation. The compositae, “Mecca”, (M.sativaspp.falcataArcemgeli) was selected for desirable noduiation and nitrogen fixation attributes. The objective of this study was to determine soil fertility factors governing its nodulation, nodule histology and cytosol enzymology essential for symbiotic nitrogen fixation. Adequate available soil P was a first limiting factor. Growth, noduiation and nitrogen fixation resulted in significant response to increases in K and Ca only with P combinations. Multiple regression for nodule cytosol plant nutrient composition was nitrogenase activity = 7.78μg P + 2.73μg K + 3.53μg Ca ‐ 6.06μg Na, R2= 0.74, C.V. = 12.7%. Distinctive coralloid nodule histology include abundant nondeterminate, apical nodule peripheral meristem regions with numerous developing anastomosic vasculars and transition cells with polyploid nuclei. Cytosol transaminase enzymology of the interstitial nonrhizobial infected cells was significantly increased for increased K levels with adequate P. Interrelationships for these nodule cytosol enzyme activity levels with multiple regression analysis was nitrogenase activity levels = 0.79 IU) Aspartate transaminase (AST) + 1.77 IU Glutamine synthetase (GS) + 0.85 IU Glutamate dehydrogenase (GDH) + 0.38 IU Glutamine‐2 oxoglutarate aminotransferase (GOGAT), R2= 0.63, C.V. = 16.8%. Favorable response to K fertilization has practical economic relevance for increased nodulation and nitrogenase activity levels with improved production of the very important forage legume alfalfa.

ISSN:0190-4167    

DOI:10.1080/01904169009364060

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Soybean plants (Glycine max[L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO‐3, 0.67 mM NO‐3plus 0.33 mM NH+4, 0.33 mM NO‐3plus 0.67 mM NH+4, and 1.0 mM NH+4) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N‐source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH+4at pH 4.5. Shoot‐to‐root ratios increased in plants which had an increased proporiton of NH+4‐N in their nutrient solutions at all levels of root‐zone pH. Uptake of NO‐3and NH+4was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO‐3plus NH+4, NH+4was absorbed at a ratio of 2:1 over NO‐3at pH 6.0. As the pH of the root‐zone declined, however, NH+4uptake decreased and NO‐3uptake increased. Thus, the NH+4to NO‐3uptake ratio declined with decreases in root‐zone pH. The data indicate a negative effect of declining root‐zone pH on NH+4uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH+4‐N at low pH is due to a decline in NH+4uptake and a consequential limitation of growth by N stress.

ISSN:0190-4167    

DOI:10.1080/01904169009364061

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Experiments were conducted with sunflower (Helianthus annuus, L.) of two inbred lines and eight cultivars grown in the field, in pots in the greenhouse or growth chamber and in nutrient solution. Water solutions of 2,3,5‐triiodobenzoic (TIBA) were sprayed over the top of the plants or added to the nutrient solution TIBA treatment resulted in induction of bract necrosis in some plants, increasing the bract necrosis index with higher TIBA concentration. TIBA had little effect on element concentration in leaves but it decreased the levels of Ca, Mg and B in bracts of plants. At a low TIBA concentration (25 μM) in the nutrient solution, young plants growing in hydroponic solution at a low Ca level, the levels of Ca and Mg of young leaves were decreased but TIBA treatment did not affect significantly the levels of these elements in roots. Since TIBA produces both bract necrosis and lower Ca content in bracts, it is suggested that bract necrosis is a physiological disorder related with lower Ca levels existing in the bracts when plants are grown under stress conditions.

ISSN:0190-4167    

DOI:10.1080/01904169009364062

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The concentration of silicon is high during the elongation phase (approximately day 1 through day 21 post‐anthesis) of cotton fiber development. The ratio of the amount of silicon per mass of fiber peaks at the time when secondary wall initiation occurs. This suggests that silicon has one or more functions during a specific phase of cotton fiber development.

ISSN:0190-4167    

DOI:10.1080/01904169009364063

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Phosphorus fertilizer management of greenhouse grown micropropagated potato plantlets has been based on field research. Differences in growing conditions, potting media and the planting material itself may make the field research data base unacceptable in a greenhouse environment. This study was conducted to determine the optimum nutrient solution phosphorus (P) concentration for maximum growth and yield of micropropagated potato plantlets grown under greenhouse conditions. Nutrient solution P concentrations ranging from 0 to 55μg P/ml were evaluated. Each nutrient solution P concentration was applied weekly to micropropagated potato plantlets that were grown in 80% vermiculite‐20% sand potting medium. Results indicate that P concentrations between 10 and 35μg P/ml are optimum for potato plantlet tuber production. This P concentration range maximizes vegetative weight, total tuber weight and number of tubers produced per micropropagated potato plantlet. Data further indicated that the potting medium retained and possibly accumulated P from the weekly applied nutrient solution. This enabled the plants, receiving relatively low nutrient solution P concentrations, to extract more P for proper growth and yield with time. To avoid unnecessary nutrient costs, the 15μg P/ml nutrient solution concentration is recommended. This P concentration will produce maximum tuber yields and still allow for less than optimum management which may cause P conversion to unavailable forms. Additional studies should be conducted to correlate plant tissue concentration at different growth stages with final tuber yields.

ISSN:0190-4167    

DOI:10.1080/01904169009364064

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169009364056

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor