THE EFFECT OF WATER STRESS OVER Pinus cooperi Blanco DURING PRECONDITIONING AT THE NURSERY

Abstract

The preconditioning through water stress, favors the mechanisms of resistance to drought of the trees once planted. An experiment was conducted in order to determine the effect of three conditions of stress through irrigation each 48, 144 and 288 hours, in the preconditioning of nine-month Pinus cooperi seedlings produced in nursery in containers of 170 mL with substrate made of peat moss (55%), vermiculite (24%) and agrolite (21%). The treatments were distributed in a completely randomized experimental design with three replications per treatment and 108 individuals in total. The test consisted of three cycles of twelve days each; four evaluations of water potential per cycle were conducted. In addition, 36 days after the start, it was recorded the seedlings morphological growth. Water potential showed statistically significant differences (p<0.05) among treatments. In the condition of irrigation every 48 hours it ranged from -0.17 to -0.29 MPa; when the irrigation was every 144 hours it ranged from -0.17 to -0.59 MPa and where irrigation was performed every 288 hours the water potential was from -0.26 to -3.24 MPa. Regarding morphology, statistical differences (p < 0.05) only existed in the variables height and strength index. The individuals subjected to water stress by up to 12 days did not significantly diminish their growth. The seedlings without watering for 144 hours presented potential associated with a low level of water stress.