Cover crops and green manures have been adopted in rainfed agriculture for providing soil protection between cultivation seasons and for increasing soil nutrient and organic matter content. A greenhouse experiment was conducted to evaluate physiological responses of the green manure Vicia sativa to drought. The gravimetric leaf water of content of 80% did not decrease during 24 days of water withholding. Gas exchange was very sensitive to drought. For instance, net CO2 uptake of 7.8 ± 0.17 ?mol m-2 s-1 started decreasing at eight days of water withholding but recovered when the plants were re-watered. While total chlorophyll was not signifi cantly degraded for the droughted plants, these individuals accumulated 1,000-fold the proline of the control, which amounted to 0.41 ± 0.09 ?mol g-1. Raman spectroscopy revealed differences in the accumulation of metabolites at 24 days of water withholding between well-watered and droughted plants, including a higher content of abscisic acid, gibberellic acid, indoleacetic acid, and zeatin. Vicia sativa can tolerate month-long droughts and can be considered as a useful alternative for increasingly arid locations.