THE RESPONSE OF CHAMAECYPARIS-NOOTKATENSIS STECKLINGS TO 7 NUTRIENT REGIMES

Yellow cypress (Chamaecyparis nootkatensis (D. Don) Spach) stecklings (rooted cuttings) of two clones from each of three provenances representing northern and southern Vancouver Island and the lower mainland, British Columbia, were grown in inert rooting medium and fertilized with seven nutrient solutions. The stecklings were compared for their growth and photosynthetic responses to (i) deficiencies of nitrogen, phosphorus, and potassium separately, or a deficiency of all three macronutrients; (ii) nutrients supplied in excess; and (iii) nutrients supplied at constant or exponentially increasing rates. One clone from the northern Vancouver Island provenance was consistently more productive than the others, having the greatest total dry weight and highest net photosynthetic rate in all nutrient treatments. The "complete" nutrient mix supplied in exponentially increasing volumes provided maximum response in growth and photosynthesis for all clones. This response was not significantly better than that of stecklings that received the complete solution at a constant rate of addition; however, stecklings supplied at a constant rate were less efficient in their uptake of macronutrients. Deficiency of nitrogen resulted in the greatest reduction in steckling growth. Phosphorus deficiency resulted in the greatest reduction in stomatal and mesophyll conductances, and therefore assimilation rate. Provided the proportions of individual mineral elements were balanced, plants subject to very low levels of nutrition survived and continued to photosynthesize. Nutrients provided in excess resulted in luxury consumption, and eventually led to plant death. This study demonstrates the potential for using nutritional testing in clonal screening trials to reveal high productivity or deficiency-susceptible clones.