COMPARATIVE RESPONSES OF CUTTINGS AND SEEDLINGS OF EUCALYPTUS-GLOBULUS TO WATER-STRESS

We compared responses of cuttings and seedlings of Eucalyptus globulus Labill. subsp. globulus to water stress in a 9-week greenhouse experi ment. Optimal water availability was achieved by watering pots daily t o field capacity, and two water stress treatments were imposed by redu cing watering frequency to every 6 or 14 days. Within each treatment, height growth rates of cuttings and seedlings were similar, but the wa ter-stress treatments reduced growth rates by up to 15%. Diameter grow th rates were 25% lower in cuttings than in seedlings under well-water ed conditions and were reduced by water stress in both plant types. Un der well-watered conditions, cuttings and seedlings used similar amoun ts of water, whereas seedlings had greater water use (up to 28.5%) tha n cuttings in both water-stress treatments. Shoot water relations of c uttings and seedlings were similar over a range of soil water contents . The responses of transpiration and stomatal conductance to soil wate r content were similar in cuttings and seedlings. At the end of the ex periment, plants were left unwatered. Seedlings that had been precondi tioned by watering every 14 days survived to lower soil water contents than seedlings from the well-watered treatment; however, cuttings fro m the water-stress treatments died at higher soil water contents than either seedlings from the same treatment or cuttings from the well-wat ered treatment. We conclude that exposure to moderate water stress doe s not effectively precondition cuttings, and that their ability to res ist extreme water stress may be limited. These characteristics are pro bably associated with the root systems of cuttings which differ develo pmentally, architecturally and anatomically from the root systems of s eedlings.