T.C. Tucker

Ammonium (15N) metabolism in cotton under salt stress

Abstract Plant growth and metabolism is impaired under stress conditions, resulting in decreased crop yields. The purpose of this investigation was to evaluate the NaCl stress effects on NH+ 4 metabolism in cotton plants at vegetative and reproductive stages of growth. Cotton (Gossypium hirsutum L.) plants grown in normal (control) and NaCl treated Hoagland solutions were analyzed for distribution of N15 in NH+ 4 plus amide‐N, free α‐amino‐N, total soluble‐N and protein‐N after the plants were provided 15NH4NO3 in nutrient solutions for 6, 12 and 24 h. The concentration of protein‐15N was enhanced under a low level of NaCl (‐0.4 MPa osmotic potential) at the vegetative growth stage. The difference between the protein‐15N concentration of the moderately salinized (‐0.8 MPa) plants and the controls was not significant. A high level of NaCl (‐1.2 MPa) significantly decreased protein‐N content of plants compared with the controls and any other level of salinity. The NaCl increased accumulation of NH4 + plus a...

Growth and chlorophyll, mineral, and total amino acid composition of tomato and wheat plants in relation to nitrogen and iron nutrition I. Growth and nutrient uptake

Abstract Plant growth and metabolism can be impaired by the nutritional status of the media in which it is grown. The present study was performed to investigate the effect of NO3‐N and FeSO4‐Fe regimes on growth, nutrient uptake, and total amino acid‐N content of tomato and wheat plants. Plants were grown in a greenhouse in sand culture with three levels of FeSO4Fe and four levels of NO3‐N. Increasing the NO3‐N up to 200 mg kg‐1 increased tomato growth. The fluctuations of total amino acid‐N, free NH4 and nutrient uptake except sodium were parallel to dry matter production. In wheat plants dry matter production continued to increase with NO3‐N addition up to 400 mg kg‐1. The increased NO3‐N supply in the nutrient solution continuously increased the free NH4, the total amino acid‐N in the plants, and P, Ca, K, and Na uptake.

Growth and chlorophyll, mineral, and total amino acid composition of tomato and wheat plants in relation to nitrogen and iron nutrition II. Chlorophyll content and total amino acid composition

Abstract Studies of the amino acids distribution in plants subjected to nutrient regimes are limited. The present study investigated the effect of NO3‐N and FeSO4‐Fe regimes on chlorophyll and total amino acids composition of tomato and wheat plants. Also the distribution of 17 amino acids between the different plant parts was studied. Increasing the NO3‐N level up to 200 mg kg‐1 greatly increased the total amino acids content of tomato plants. The total amino acids content of wheat plants continued to increase with addition of NO3‐N up to 400 mg kg‐1. The response of chlorophyll content to NO3‐N supply was highly dependent on Fe level both in tomato and wheat plants. The interaction between NO3‐N and FeSO4‐Fe had a great effect on the total amino acids content and distribution. Iron increased the translocation of proline from roots to leaves. The overall amino acids contents of leaves was higher than that of stems or roots.

Determining phosphorus needs for cabbage grown on calcareous soils

Abstract Cabbage (Brassica olearacea var. capitata L.) yield differences from added P were highly significant up to the predicted response level of 0.4 mg 1 . The increases in yield were basically due to larger head sizes. No statistical differences were found after the soil P levels were adjusted above 0.4 ppm, as determined by P isotherms constructed from initial soil samples. Slight differences occurred between years, but likely were due to cultivar growth differences. Data show that the isotherm predicted level fits rather closely the P requirements for cabbage as related to crop yields. Since extraction methods measure only the intensity factor of P, these methods could lead to incorrect P fertilization recommendations. The absorption of P is progressively reduced as the temperature goes down.