Early Rooting Response of Choke Cherry Seedlings to a Commercial Extract of the Marine Alga Ascophyllum nodosum

Choke cherry (Prunus virginiana L.) is an ecologically important species in the reclamation of Canada’s oil sands because of its extensive lateral root system that readily suckers and thus quickly creates dense thickets. Consequently, choke cherry provides rapid site occupancy that re-establishes nutrient cycling and prevents erosion, as well as providing food, shelter, and nesting for wildlife. Our goal is to increase root growth after spring planting on reclamation sites by improving seedling root system quality. As increased rooting during seedling establishment has been reported in various horticultural nursery crops treated with Ascophyllum nodosum (L.) Le Jolis extract (ANE), we hypothesized that ANE applications would create a well-developed root system in young choke cherry seedlings. We present results from the initial phase of the study here. The objective of this phase was to determine whether and, at what rate, ANE would increase rooting in choke cherry seedlings during the establishment phase of containerized culture. We transplanted germinants from two Alberta seedlots, arising from a study to improve germination of choke cherry seed, to individual cells of the Ray Leach "Cone-tainer" Single Cell System filled with a 1:1 peat:vermiculite media. Trays with cells were placed in a Conviron walk-in chamber maintained at 25/20°C day/night under a 16-h photoperiod at a relative humidity of 85%. After a 2-week acclimation period to chamber conditions, we applied ANE in deionized water twice at the following rates: 0 ml/L, 0.25 ml/L, 0.5 ml/L, 1.0 ml/L, and 2.0 ml/L. Two irrigations with dechlorinated water separated the ANE applications. One week after the second application, we harvested seedlings and washed roots free of media. Then, we counted secondary and tertiary roots and measured lengths of secondary roots. Root system morphology of both seedlots was affected by ANE application, but there were seedlot differences. For the seedlot that was more responsive to ANE, secondary roots were longer and tertiary roots were more numerous in response to the 0.25- and 0.5-ml/L rates compared with 0.0- and 1.0-ml/L rates. Although the 2.0 ml/L rate increased the number of secondary roots compared with the other rates, they were shorter and lacked tertiary roots.