This was the conclusion of Mara Dolores Glvez in defending her PhD thesis at the Public University of Navarre. Her PhD was entitled, "Nodule metabolism in Pisum sativum L. in response to water stress: carbon/nitrogen interactions and the possible molecules involved in the modulation of the response".

Nitrogen-fixing and drought

Biological nitrogen-fixing is a process of great agricultural and ecological interest, given that nitrogen, after water and carbon, is the nutrient that most limits vegetable growth and crop production. This process is particularly sensitive to adverse environmental conditions, such as water stress or drought. This is why Mara Dolores Glvez's PhD was aimed at investigating how the regulation of biological nitrogen-fixing is carried out under drought conditions.

The reduction of atmospheric nitrogen to ammonia - or nitrogen-fixing - can only be carried out by procariots. Amongst these, the ones generically known as rhizobes are capable of establishing symbiosis with legume plants giving rise to a new structure: the nodule.

On the one hand, the plant benefits from the micro-organism, that takes on the task of capturing nitrogen from the air and converting it into ammonia in such a way that the plant can use it. This ammonia is incorporated into carbon skeletons in order to form aminoacids and proteins. On the other hand, the micro-organism obtains nutrients necessary for its growth from the plant.

Under drought conditions, a reduction in nodule sacarose synthesis activity was observed. This drop occurred simultaneously with a decrease in nitrogen-fixing, enabling the establishment of a high correlation between both processes in adverse conditions. As a consequence of the inhibition of sacarose synthesis activity, a drop in the concentration of phosphate sugars
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Contact: Garazi Andonegi
garazi@elhuyar.com
34-94-336-3040
Elhuyar Fundazioa
4-Feb-2005