Comparison of drought tolerance in nitrogen-fixing and inorganic nitrogen-grown common beans

LODEIRO, A.R.; GONZÁLEZ P.; HERNÁNDEZ A.; BALAGUÉ L.J.; FAVELUKES G.

PLANT SCIENCE

Elsevier

Año: 2000 vol. 154 p. 31 - 41

0168-9452

In this work, we evaluated how the use of alternative N sources affects drought-stress tolerance in common beans. To this end, plants were cultivated employing either N2 fixation or two levels of inorganic nitrogen: 1 mM NH4NO3 (limiting) or 10 mM NH4NO3 (sufficient). Drought was imposed by withholding watering at 30 days after planting (DAP)–coinciding with flowering. At 20 DAP, growth and N content were significantly higher in NH4NO3-sufficient plants than in N2-fixing and NH4NO3-limited beans. At later times, only N2-fixing and NH4NO3-sufficient plants continued assimilating N and growing, with the NH4NO3-sufficient plants being consistently bigger. After 10 days of stress (40 DAP), desiccation was evident, but only NH4NO3-sufficient plants suffered drought-induced senescence. After  20 days of stress (50 DAP), N content increased in NH4NO3-sufficient but not in N2-fixing beans, despite the latter's lesser state of wilt. Pod dry weight dropped 43% in NH4NO3-sufficient beans with respect to well-watered plants, while remaining constant in N2-fixing beans. Under drought conditions, the number of pods limited pod yield regardless of the nitrogen source used; nevertheless, the translocation of soluble matter to pods continued in both NH4NO3-sufficient and N2-fixing beans. We conclude that common beans grown under conditions of N2 fixation were more drought-tolerant than those provided with sufficient levels of NH4NO3. The most stress-sensitive traits in these plants were the incorporation of N into their shoots and the number of pods remaining on them.