Gas exchange, water relations and morphology of yellow-cedar seedlings and stecklings before planting and during field establishment

Information is lacking on how yellow-cedar (Chamaecyparis nootkalensis (D. Don.) Spach) stecklings compare with seedlings in their response to potentially limiting field site environmental conditions. Before planting, yellow-cedar seedlings and stecklings were characterized at 5 and 22 degrees C root temperatures for gas exchange parameters (n = 6), root growth capacity (n = 12) and plant water movement (n = 6) using a fully randomized design in a controlled environment growth room. Seedlings, compared with stecklings (t-test), showed a faster (p = 0.01) recovery of net photosynthesis (Pn) and stomatal conductance (gwv) after root temperature increased from 5 to 22 degrees C. Seedlings had greater (p = 0.05) root growth capacity (number of new roots greater than or equal to 0.5 cm in length) than stecklings after 14 days at 22 degrees C and after 14 days at 5 degrees C followed by 15 days at 22 degrees C. Seedlings had a lower (p = 0.01) resistance to plant water movement measured after 29 days (14 days at 5 degrees C followed by 15 days at 22 degrees C root temperature). Seedlings and stecklings were planted on a coastal British Columbia field site and monitored for 1) morphological development and physiological response to ambient site conditions throughout the first growing season, and 2) physiological response to drought conditions during late summer. Both trials used a fully randomized design and stock type means were compared using t-tests (p = 0.10, 0.05, and 0.01). Initially, seedlings were taller (p = 0.01) than stecklings but otherwise morphologically similar (n = 20). Over a 35 week period after planting, stecklings had greater incremental height growth, while seedlings produced a greater (p = 0.01) number of roots extending out of the root plug. Seedlings and stecklings (n = 6) had similar Pn and gwv patterns under late spring environmental conditions. However, seedlings had greater Pn and gwv under cold temperature (p = 0.05 and p = 0.1, respectively) and drought conditions (p = 0.05 and p = 0.01, respectively), but during conditions of high evaporative demand and adequate soil moisture, stecklings had greater (p = 0.01) Pn and gwv. Seedlings had higher (p = 0.01) daily integrated shoot water potential values (D psi) at different times during the growing season, and maintained higher (p = 0.05) predawn (psi pd) shoot water-potential values, higher (D psi) (p = 0.01) resistance to plant water movement (R(SPAC)) during the drought conditions.