Effects of water stress on the physiology and morphology of black locust trees, Robinia pseudoacacia, in Algeria

Abstract

Irregular rainfall and high temperatures are factors limiting the growth of plant species living in arid zones in Algeria. This results in a reduction of the plant cover, favouring desertification. Plan-ting drought-resistant species is a clear advantage for the restoration of plant cover and the fight against soil erosion in these areas. Black locust trees (Robinia pseudoacacia L.) belong to the family of nitrogen-fixing legumes, which makes them suitable for colonising mine-ral-poor soils. Thanks to its rapid vege-tative propagation, this species could re-colonise areas threatened by drought. It is important to study the physiological behaviour of R. pseudoacacia seedlings under water stress conditions to assess the drought resistance of the species, as well as its capacity for survival in areas with low rainfall. After ten weeks of growth, watering of the R. pseudoacacia seedlings was stopped for four weeks. After two weeks, a significant decrease in growth was observed and the formation of new leaves ceased. The relative water content of the leaves (RWC) decreased steadily during the same period to 78%, then fell abruptly after four weeks without watering. A significant decrease in stomatal conductance was observed from the second week without watering, which reduced the quantity of water lost through stomatal transpiration. When watering resumed, growth recovered and an increase in water content and sto-matal conductance of the leaves of the stressed plants was observed after one week. This species thus appears to have a high capacity for resuming normal physiological activity after a four-week inter-ruption of watering.