Search Results - (Author, Cooperation:T. W. Rufty)

2012-09-01

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Carbon/*metabolism ; Carbon Dioxide/*metabolism ; Mycorrhizae/*metabolism ; Nitrogen/metabolism ; Plant Development ; Plants/microbiology ; *Soil Microbiology

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

A study was conducted to examine the hypothesis that the effects of external Al on NO3− uptake and assimilation depend upon the concentration of Al present. Young soybean seedlings [Glycine max (L.) Merrill, cv. Essex], growing under moderate acidity stress at pH 4-2, were exposed to a range of {A13+} in solution for 3d, and to labelled 99 atom %15NO3− during the final hour of Al exposure. Uptake of 15NO3−g−1 root dry weight was increased by about 28% in the presence of Al at {A13+} below 10 mmolm−3, and NO3− uptake was decreased by about 12% when the {A13+} increased to 44mmoln−3. The stimulation phase closely paralleled stimulation of root elongation. At higher {A13+}, the inhibition of root elongation was much more severe than that of NO3− uptake. There was no indication of a separate effect of Al on root 15NO3− reduction in situ, as the accumulation of reduced 15N in the root remained a similar percentage of 15NO3− uptake at all {A13+}. At higher {A13+}, the atom %15N enrichment of the insoluble reduced-N (protein) fraction of root tips increased. This suggests that the Al inhibition of root elongation did not result from disruption of the N supply to the root apex.

Electronic Resource

1399-3054

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Studies were conducted to identify and compare diurnal changes in sucrose phosphate synthase (EC 2.4.1.14) activity in leaves of different species, and the effect of nitrogen nutrition on the rhythm in soybean [Glycine max (L). Merr] leaves. In recently expanded corn (Zea mays L.) leaves, a single peak of enzyme activity was observed at the beginning of the photoperiod. A similar pattern was observed in older corn leaves, but activities (leaf fresh weight basis) were lower. In recently expanded pea (Pisum sativum L.) and soybean leaves, two peaks of sucrose phosphate synthase activity were observed over a 24-h light:dark period, one at the beginning and one at the end of the photoperiod. A similar pattern was observed in older soybean leaves, but activities were generally lower and the amplitude of the changes was reduced. In a separate experiment, soybean plants were grown in the greenhouse with either 2 or 10 mM nitrate. The high-N plants had higher rates of photosynthesis and translocation, and greater activities of sucrose phosphate synthase in leaf extracts, compared to low-N plants. Over both experiments with soybeans, changes in sucrose phosphate synthase activity during the photoperiod were closely aligned with changes in translocation rate.

Electronic Resource

1573-1561

Insecta ; tobacco hornworm ; Manduca sexta ; tobacco ; Nicotiana tabacum ; ozone ; weather fleck ; Lepidoptera ; Sphingidae

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract Tobacco plants, Nicotiana tabacum were grown under different levels of ozone (O3) in open-top chambers. Ozone concentrations were established by charcoal filtration, which reduced O3 to approximately one-half ambient, or by the addition of O3 to unfiltered air to increase concentrations to approximately 1.4 or 1.7 times ambient O3. Survival of tobacco hornworm, Manduca sexta, larvae was increased when second instars were fed tobacco leaves grown in chambers with elevated levels of O3. Second instars also gained significantly more weight when they were fed for one week on plants exposed to elevated levels of O3 than when they were fed plants grown in charcoal-filtered air. Ozone-treated tobacco plants had higher levels of total nitrogen (primarily reduced nitrogen) and soluble carbohydrates (sugars), and lower levels of leaf-surface components, starch, nicotine, and rutin. Increased survival and growth response of hornworm larvae to elevated O3 levels in these experiments suggests that similar responses could occur in the southeastern US tobacco production areas where O3 levels can be high enough to injure tobacco plants.

Electronic Resource