摘要:

The relationship between acid phosphatase activity (APA) and phosphorus (P) stress in two bean genotypes(Phaseolus vulgarisvar Tacarigua and var Manuare) and in cowpea(Vigna unguiculatavar TUY) are reported in this paper. Sand culture experiments were performed in a highly ventilated greenhouse where plants were drip feed with nutrient solutions with either 1.0 or 0.02 mM P. Acid phosphatase activity was determined in extracts from roots, young (apical) and mature leaves, and in leaf discs and root sections using o‐carboxyphenyl phosphate as substrate. Differences in total dry matter were found to be significant (P = 0.01) only for cowpea. However, reduction in leaf area was significant in both species and varieties. Differences in the P concentration in the dry matter, were large enough to suspect that plants were suffering from a mild P stress. Acid phosphatase activity was above the values reported for these species under P stress, however, APA in these legumes appears not to be inducible by the low P‐concentration level used in this study. A higher APA was found in young as compared to mature leaves, and the expression of APA also showed intraspecific variation. Acid phosphatase activity was related to the age of the leaves and was easily measured in leaf discs, specially for bean. This and the ratio of P concentration between young and mature leaves may be an alternative to absolute P‐status determination in plants.

ISSN:0190-4167    

DOI:10.1080/01904169409364723

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of two titanium (IV) compounds, titanium ascorbate and titanium chloride, on some enzymatic activities, such as catalase, peroxidase, lipoxygenase and nitrate reductase in seeds, embryos, and seedlings and adult plants of red pepper(Capsicum annuumL.), was studied. A stimulatory effect of titanium was observed for every iron‐depending enzyme studied at all developing stages as well as for nitrate reductase but only for whole plants. This occurs because Ti+3/Ti+4catalizes the activity of iron and enhances iron‐dependent enzymes.

ISSN:0190-4167    

DOI:10.1080/01904169409364724

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Toxic effects of aluminium (Al) on root tips are considered to decrease export of cytokinins to shoots, and deficiency of cytokinins has been made responsible for Al‐induced inhibition of shoot growth. But no experimental data on the influence of Al on endogenous cytokinin levels in higher plants have been reported. In this study, the endogenous levels of zeatin riboside (ZR) and dihydrozeatin riboside (DHZR) of roots, stems, and leaves of two bean cultivars(Phaseolus vulgarisL. cv Contender and cv Strike) exposed to Al in continuously flowing nutrient solution (pH 4.5) was analysed. The supply of a high Al concentration (sum of monomeric Al species, 127 μM) caused severe inhibition of root elongation in both cultivars. The cv Strike was more affected by both Al‐induced mineral nutrient disorders and Al‐induced alteration of leaf water relationships. In both cultivars Al‐supply significantly increased ZR and DHZR. Leaves of Al‐treated plants exhibited a more than three times higher concentration of ribosylated cytokinins than controls. Nevertheless, stomatal resistance was significantly increased by Al in both cultivars. Our results support the hypothesis that Al affects plants not by inducing deficiency of cytokinins but of some other factor necessary for the manifestation of cytokinin action.

ISSN:0190-4167    

DOI:10.1080/01904169409364725

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The question of whether a direct (uninterrupted) contact between plant roots and solid substrate is a prerequisite for the mobilization of sparingly soluble iron (Fe) by plant roots was investigated. Factorial combinations of two types of contact between the roots and rooting medium [direct or interrupted (roots placed inside a dialysis tube (DT)], two rooting media (nutrient solution or vermiculite), and two Fe supply conditions [without soluble Fe (control) or plus Fe‐EDDHA] were investigated. Placing the roots inside DT, with no visible mechanical impedance for the root, reduced the growth of tops and roots in most cases. Iron mobilization, judged by the total amount of Fe in the tops, strongly decreased if roots were enclosed in DT. This was true in plants grown in vermiculite as well as in nutrient solution containing Fe‐EDDHA. It is concluded that a direct contact between the surface of root cell walls and the Fe substrate is a prerequisite for the Fe mobilization by the plant roots.

ISSN:0190-4167    

DOI:10.1080/01904169409364726

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Nutrient uptake by snapdragon(Antirrhinum majusL. ‘Peoria') was compared at five root‐zone temperatures: 8, 15, 22, 29, and 36°C. Uptake of nitrate (NO3‐‐N), ammonium (NH4+‐N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), iron (Fe), manganese (Mn), and zinc (Zn) responded quadratically to increasing root‐zone temperature. Greatest nutrient uptake temperature varied with nutrient but ranged from 15 to 29°C. Uptake of copper (Cu) and molybdenum (Mo) were unaffected by root‐zone temperature. Dry weight gain and stem length also responded quadratically to increasing root‐zone temperature. Optimal temperatures for nutrient uptake and growth were similar, averaging 22°C. These results indicate increasing or maintaining root‐zone temperatures near 22°C maximizes growth and nutrient uptake of snapdragons.

ISSN:0190-4167    

DOI:10.1080/01904169409364727

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Aluminum (Al) toxicity was studied in two tomato cultivars(Lycopersicon esculentumMill. ‘Mountain Pride’ and Floramerica') grown in diluted nutrient solution (pH 4.0) at 0, 10, 25, and 50 μM Al levels. In the presence of 25 and 50 μM Al, significant reduction was found in leaf area, dry weight, stem length, and longest root length of both cultivars. Growth of ‘Floramerica’ was less sensitive to Al toxicity than growth of ‘Mountain Pride’. Elemental composition of the nutrient solutions were compared immediately after the first Al addition and four days later. The uptake of micronutrients copper (Cu), manganese (Mn), molybdenum (Mo), zinc (Zn), boron (B), and iron (Fe) from the nutrient solution was reduced in both cultivars with increasing Al levels. Nutrient solution Al gradually decreased in time for every treatment; less in cultures of ‘Floramerica’ than in ‘Mountain Pride’. Aluminum treatments decreased the calcium (Ca), potassium (K), magnesium (Mg), Mn, Fe, and Zn content in the roots, stems, and leaves. Aluminum treatment promoted the accumulation of P, Mo, and Cu in the roots, and inhibited the transport of these nutrients into stems and leaves. At 25 and 50 μM levels of Al, lower Al content was found in the roots of cv. “Floramerica’ than in the roots of cv. ‘Mountain Pride’.

ISSN:0190-4167    

DOI:10.1080/01904169409364728

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of aluminum (Al) toxicity on leaf gas exchange, leaf chlorophyll content, and sucrose metabolizing enzyme activity of two tomato cultivars(Lycopersicon esculentumMill. ‘Mountain Pride’ and ‘Floramerica') was studied to determine the mechanism of growth reduction observed in a related study (Simon et al., 1994, Part 1). Plants were grown in diluted nutrient solution (pH 4.0) with 0, 10, 25, or 50 μM. Al for 16 days. Leaf gas exchange was reduced 2–3 fold in both cultivars as Al concentration increased. Gas exchange of ‘Mountain Pride’ was more sensitive to Al toxicity than ‘Floramerica’, agreeing with growth responses observed. Reductions in carbon dioxide (CO2) assimilation rate appeared to be due to nonstomatal factors in ‘Floramerica’, but stomatal and non‐stomatal limitations in ‘Mountain Pride’. Chlorophyll content of leaves was not affected by Al. Acid invertase (AI) and neutral invertase (NI) activity of roots responded consistently to Al concentration in both cultivars. Root AI and NI activity decreased to a greater extent for ‘Mountain Pride’ than for ‘Floramerica’.

ISSN:0190-4167    

DOI:10.1080/01904169409364729

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In pot experiments, uptake of zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn) by hybrid rice from different soil types was compared with a traditional rice(Oryza sativaL.) cultivar. The concentration and total uptake of Fe in the shoots of hybrid rice grown in Oxisol and Ultisol were lower than those of the traditional cultivar. The concentration and total uptake of Zn in the shoots of hybrid rice grown in the Inceptisol (calcareous) were significantly higher than those of the traditional cultivar. Higher ratios of Zn and Fe in upper leaves (UL) to the lower leaves (LL) were found in hybrid rice grown in the calcareous Zn‐deficiency soil. The results indicated that hybrid rice root avoided absorbing excess Fe from Fe‐toxic soils due to its higher oxidizing power, and was more efficient in absorbing Zn from calcareous Zn‐deficient soils than the traditional cultivar.

ISSN:0190-4167    

DOI:10.1080/01904169409364730

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Plantlets of the winter‐hardy ‘John Franklin’ rose cultivar, derived from nodal sections of greenhouse‐grown plants, were cultured on a modified MS medium. The kinetics of P uptake for 96 h as a function of medium temperature was studied by using32P. Rooted plantlets absorbed significantly (P < 0.01) greater amounts of P at 22°C compared with non‐rooted ones and uptake was linear with time for both. P uptake was also significantly higher (P < 0.05) for rooted versus non‐rooted plantlets at 33°C but no significant difference was observed at 3°C. The results show that roots, previously thought to be mostly non‐functional in nutrient uptake on a culture medium, played a key role in absorbing P at 22 and 33°C.

ISSN:0190-4167    

DOI:10.1080/01904169409364731

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Aluminum (Al) toxicity to plants in complete nutrient solutions is difficult to relate to Al activity in solution because of precipitation and complexation. Aluminum toxicity was studied for two seedling crops, sorghum(Sorghum bicolorL. Moench) and wheat(Triticum aestivumL. em Thell), at low levels (≤10 μM) in two incomplete nutrient solutions to study plant response to Al alone, Al+PO43‐, Al+OH‐, and Al+PO43‐+OH‐. Relative root length was the bioassay for Al toxicity. ‘Monomeric’ Al was measured using Aluminon and both root length and measured Al were compared to the theoretical Al in solution predicted by the MINTEQA2 equilibrium model.

ISSN:0190-4167    

DOI:10.1080/01904169409364732

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor