Effects of half-sib family selection on the root regeneration potential and initial landscape establishment of container-grown sycamore, Platanus occidentalis (L.)

Abstract

occidentalis (L.), were grown in 9.1 liter containers and transplanted in field plots at College Station, Texas, at three different seasons (fall, spring, and summer). Summer transplanting was most stressful, with 46 % seedling mortality across families, and mean reduction in height (dieback) across families of-87 cm, compared to 100 % and 98 % survival and 61 cm and 28 cm shoot extension for fall and spring transplants, respectively. Texas seedlings out-performed more geographically distant selections both in the nursery and field. TFS-09 and Brazos-C (field) were greater in initial and final heights and calipers, change in height and visual ratings. Four half-sib families grown in 4.7 liter containers (completely randomized design) were transplanted to root observation boxes concurrent with the field study for root regeneration potential determinations. Across seasons, Brazos-C required fewest days to initiate root regeneration, TFS-09 was taller than W-1 4 and Putnam, and TFS-09 and Brazos-C had greater caliper than WV-14 and Putnam. TFS-09 regenerated more root surface area, and TFS-09 and Brazos-C had the greatest number and length of regenerated roots in spring. TFS-09 and Brazos-C had larger transplanted Footballs and shoot mass. Gas exchange was determined on ten seedlings each of 2.8 liter container grown TFS-09 and Putnam under well watered and simulated drought stress conditions. Drought stress decreased all measurements across families. TFS-09 maintained a more favorable whole plant transpiration and water use efficiency under water stress than Putnam. Transplant season and half-sib family influenced landscape establishment and RRP. Selection of locally adapted half-sib families for seed source by nursery growers could provide them, landscape designers, and contractors potential economic benefits in the form of reduced production costs and increased growth in the nursery and during landscape establishment. Days to first regenerated roots in observation boxes were the RRP characteristic best corresponding to success during the first post-transplant growing season in the field.