Root System Development and Seed/Oil Productivity in Safflower Under Water Stress

Safflower, Carthamus tinctorius, presents a high economic value, seeds rich in polyunsaturated and monounsaturated fatty acids, are important in the paint, biofuels and fuel additives industries. The species is adapted to climatic adversities, especially droughts, therefore we postulated that safflower would have a relatively high development and oil yields under water stress conditions. We compared three cultivars, S333, S518 and S719 under water stress starting in different development stages: vegetative (V), late vegetative (V1), flowering (F), late flowering (F1), fruiting (FR). Plants were subjected to either water treatments of decrease to 20 (at different development stages) or 100% soil capacity. Root development was significantly more pronounced in S518 F and in S719 in all stages except V, evidencing higher length, surface area, average diameter and total volume. In S333 there were more variations with greater root development in V1. The photosynthesis, stomatal conductance and transpiration rates decreased in all plants under water stress, except at the end of the life cycle, being equivalent between the treatments F1, FR and the Control group due to plants senescence. However, despite the decrease in physiological rates, seed yield and oil content were higher in cultivars S518 and S719 in treatment F and in cultivar S333 in V1. The amount of oil in the seeds was similar between the cultivars and was from 32 to 39%, being smallest in S333, as well as the seed productivity. The data showed that water stress favored seed production and oil content in all cultivars studied and it should start during the flowering period of cultivars S518 and S719. These data can be relevant for large-scale cultivation, since it can be economical in water resource, with higher productivity, low damage to the root system and reduced production costs.