Nutrient Availability For Uptake Research Articles

Nitrogen translocation between clonal mother and daughter trees at a grassland–forest boundary

There is abundant evidence from short-term experiments using herbs that nutrients can be translocated from mother ramets to daughter ramets, but there is little long-term evidence from woody plants. Here, we examine translocation in field populations of a clonal tree over two growing seasons. We applied 15N to mothers or daughters in clones of Populus tremuloides at the northern edge of the North American Great Plains, where mother ramets form closed-canopy stands on relatively nutrient-rich soils, and daughter ramets occur nearby in relatively nutrient-poor grasslands. Unlabeled daughters in clones with labeled mothers had δ15N values significantly greater than those in unlabeled clones, confirming translocation from mothers to daughters. However, unlabeled mothers in clones with labeled daughters also had δ15N values significantly greater than those in unlabeled clones, indicating translocation from daughters to mothers. Further, the total foliage accumulation of added 15N was significantly (c. 10×) greater in mothers than in daughters, suggesting that more N was translocated from daughters to mothers, than from mothers to daughters. Thus, 15N moved both from mothers to daughters and from daughters to mothers, with net flow toward mothers. Because long-lived woody ramets in the field face nutrient competition from other ramets, interspecific neighbors, and soil microbes, the environmental availability of nutrients for uptake may be low for both mother and daughter ramets, causing translocation within a clone to be toward larger ramets with greater demand.

The effect of plant-associative bacteria ( Azospirillum and Pantoea) on the fruit quality of sweet pepper under limited nitrogen supply

This study investigates the influence of a commercial product, Biopron ®, consisting of the bacteria Azospirillum brasilense and Pantoea dispersa on sweet pepper fruits ( Capsicum annuum L.) under limited N supply. When the N supply was reduced from 12 (control) to 7 mmol L −1, the concentration of total-N in the fruits was significantly reduced in both inoculated and non-inoculated plants. The N supply or inoculation did not affect the dry matter content or fruit firmness, but non-inoculated fruit with low N showed a decrease in pericarp thickness and a significant increase in the color parameter a * compared with the control. Under limited N, inoculation increased the concentration of citric, ascorbic and succinic acids in green fruit compared with non-inoculated fruit, which showed lower values than control fruit. At a later (yellow) stage of development, only succinic acid showed a response to inoculation. Fruit peroxidase (EC 1.11.1.7) activity in fruit of inoculated plants was lower than that observed for non-inoculated fruit grown at both high- and low-N. In contrast, in yellow fruit, total phenolic compounds were increased under N limitation, with no inoculation effect. Our study shows that the effect of plant associative bacteria is not directly related with the increased potential availability of nutrients for uptake, especially for fruit quality characteristics.