Influence of water deficits on the water relations characteristics and productivity of wild and cultivated sunflowers ( Helianthus annuus/nuttallii/petiolaris).

The effects of water deficits on the water relations characteristics and yield of two cultivated Helianthus annuus lines, Hysun 31 and Seneca, and 2 wild Helianthus species, H. nuttallii and H. petiolaris were compared. In unirrigated plants, water deficits increased in all species during the first month after sowing (period I), were relieved by rain in the second month (period II) and then increased progressively in the final month (period III). The osmotic potential at full turgor of unirrigated plants, estimated by pressure-volume curves, decreased by 0.12-0.22 MPa during periods I and III in the cultivated sunflowers, but did not decrease significantly in the wild sunflowers.-from Authors