Influence of nursery culture on growth, cold hardiness, and drought resistance of yellow cypress

The influence of short-day (9 h) and long-day photoperiods (18 h), and three levels of plant moisture stress (none and dried to predawn shoot water potentials of −1.0 or −1.8 MPa), applied for 7 weeks beginning in mid-July 1990, were studied on greenhouse-grown stecklings (rooted cuttings) of yellow cypress (Chamaecyparisnootkatensis (D. Don) Spach). A series of morphological and physiological measurements were made on the stecklings during and after the treatment period. Moisture stress significantly reduced steckling shoot growth and shoot dry weight by lowering net photosynthesis rates, while short-day photoperiods did not. The most pronounced growth reductions occurred when the treatments were combined, but effects were short-lived, with shoot growth resuming soon after the treatments ended. The short-day and moisture-stress treatment had no significant effect on root dry weight, shoot/root ratio, or water balance ratio. The risk of using moisture stress to control shoot growth in the nursery was low;...