Elaeagnus pungens Thunb., Ligustrum japonicum Thunb., Photinia ×fraseri `Red Top', and Rhododendron sp. `Fashion' (azalea) growing in 10.4-liter containers were irrigated only at dawn with overhead impact sprinklers or pulse-irrigated three or four times each day with a drip system. Plant water potential was measured diurnally each week for 24 weeks, and growth was measured at the end of the growing season in December. Overhead irrigation resulted in less growth of all species than plants maintained near 100% container moisture with pulse irrigation. With the exception of photinia, more growth was associated with significantly lower daily accumulated water stress. Water stress of overhead-irrigated plants was generally not severe enough to cause stomata1 closure.
R.C. Beeson Jr.
Photinia plants produced in 11.4-liter polyethylene containers using a pine bark-based medium were transplanted into a well-drained sand and irrigated on alternate days. Polyethylene barriers were placed under half the root balls at transplanting to limit gravitational water loss. Plant water potential was measured diurnally between irrigations, and root growth was determined at 4-month intervals. Plants with barriers averaged higher cumulative daily water stress than control plants over the year, although predawn and minimum water potentials were similar. Growth index and trunk diameter were similar for the plants over barriers and controls, but the former were taller after 1 year. Plants with barriers had twice the horizontal root growth into the landscape site as control plants, resulting in twice the root mass in the landscape after 1 year.
R.C. Beeson Jr.
Large (≈5 m high) Quercus virginiana Mill. (live oak) trees produced in 0.64-m-diameter in-ground fabric containers were root pruned or not root pruned inside containers before harvest. Harvested trees were grown in two sizes of polyethylene containers for 10 months, then transplanted into a landscape. Water potential (ψT) of small branches (<4 mm in diameter) was measured diurnally during containerization and for 1 year in the landscape. Root pruning had no influence on postharvest survival. Neither root pruning nor container size affected tree water status during containerization or in the landscape. All surviving trees recovered from transplant shock following harvest after 16 weeks in a container, independent of treatment. In the landscape, 35 weeks of daily irrigation were required before dusk ψT declined to within 0.1 MPa of predawn values, a result indicating alleviation of transplant shock. Trunk growth rate during containerization was highest in larger containers. However, in the landscape, root pruning and small containers were associated with higher trunk growth rate. Tree water status during containerization and in the landscape is discussed.
R.C. Beeson Jr.
Growth characteristics and marketing of woody ornamentals prevent crop scheduling common in floriculture crops. However, many tasks in the production of woody ornamentals require coordination with the season and/or physiological state of the species. Since most woody ornamental nurseries produce many species or cultivars, a variety of tasks occur concurrently. This review highlights the major tasks required during production for most species of woody plants. The physiological and environmental factors that dictate or influence scheduling are discussed.
R.C. Beeson Jr.
Rooted photinia (Photinia ×fraseri) cuttings and hare-root slash pine (Pinus elliottii Engelm.) seedlings were transplanted initially into 0.9-, 2.9-, and 10.2-liter containers. A subset of these plants was transplanted from 0.9- and 2.9-liter containers into the next larger container size in the series (upcanning) until representative plants of each initial container size were growing in 10.2-liter containers. The photinia experiment was conducted with two fertilizer regimes [soluble vs. controlled-release (CR) fertilizer] superimposed. When CR fertilizer was used, upcanning from 2.9- to 10.2-liter containers produced the largest photinia. However, for pine, there was no advantage due to upcanning. When soluble fertilizer was used, photinia initially transplanted into 0.9-liter containers and upcanned to 2.9- and then to 10.2-liter containers had superior growth compared to those of other fertilizer × container combinations. Upcanning generally maintained or increased plant growth rate, while growth rates of plants kept in the same container generally declined the second season. Improved efficiency of the root system in nutrient absorption of upcanned plants is proposed as the mechanism for this response.
R.C. Beeson Jr.
Three species of woody ornamentals, Viburnum odoratissimum Ker Gawl, Ligustrum japonicum Thunb., and Rhaphiolepis indica Lindl. were transplanted from 3.8-L into 11.4-L containers and grown for 6 months while irrigated with overhead sprinkler irrigation. Irrigation regimes imposed consisted of an 18-mm-daily control and irrigation to saturation based on 20%, 40%, 60%, and 80% deficits in plant available water [management allowed deficits (MAD)]. Based on different evaluation methods, recommendations of 20%, 20%, and 40% MAD are supported for V. odoratissimum, L. japonica, and R. indica, respectively, for commercial production. Comparisons of plant growth rates, supplied water, and conversion of transpiration to shoot biomass are discussed among irrigation regimes within each species. Comparisons of cumulative actual evapotranspiration (ETA) to either shoot dry mass or canopy volume were linear and highly correlated. Results indicated there were minimum cumulative ETA volumes required for plants to obtain a specific size. This suggests that irrigation regimes that restrict daily ETA will prolong production times and may increase supplemental irrigation requirements. Thus the hypothesis that restrictive irrigation regimes will reduce irrigation requirements to produce container plants is false due to the strong relationship between cumulative ETA and plant size.
R.C. Beeson Jr. and G.W. Knox
Volume of water captured in a container as a function of sprinkler type, spacing, plant type, and container size was measured for marketable-sized plants. Percent water captured was calculated and a model to predict this value derived. Percent water captured was inversely related to the leaf area contained in the cylinder over the container when containers were separated, and with total plant leaf area at a pot-to-pot spacing. This relationship was independent of leaf curvature (concave vs. convex). Canopy densities were less related to percent water captured than leaf areas. Irrigation application efficiencies separated by spacing ranged from 37% at a close spacing to 25% at a spacing of 7.6 cm between containers. Container spacing, canopy shedding, and possibly some canopy retention of water later lost by evaporation were determined to be the main factors associated with the low efficiencies. The results suggest that higher irrigation application efficiencies would be maintained only if plants were transplanted to larger containers before reaching maximum canopy size rather than spacing existing containers to achieve more room for canopy growth.
R.C. Beeson Jr and M.E.D. Graham
The effect of prolonged CO2 enrichment on the activities of ribulose l,5-bisphosphate carboxylase/oxygenase (Rubisco) and carbonic anhydrase (CA) of greenhouse roses were studied. Plants of Rosa × hybrids `Red Success' were grown for 2 years at ambient and 900 μl CO2/liter during winter and spring with 75 μmol·m-2·s-1 photosynthetically active radiation supplemental lighting for 2 years. Measurements of initial and Mg+2-CO2-activated activities of Rubisco and CA were made during shoot development and at different positions within the plant canopy. Generally, there were no significant differences measured in the enzyme activities between the two CO2 concentrations. The results suggest that the photosynthetic capacity did not change and that there were no characteristic adaptations to long-term growth (up to 20 weeks) at elevated CO2 concentrations. The maintenance of Rubisco and CA activities with prolonged exposure to CO2-enriched atmospheres is proposed as the reason for long-term yield increases in roses when grown in enriched environments.
R.C. Beeson Jr. and W.M. Proebsting
The role of scion water relations was studied using Colorado blue spruce (Picea pungens Engelmann ‘Hoopsi’) scions on Norway spruce [Picea abies (L.) Karst.] rootstocks grown either in a greenhouse or in a covered, unheated lath house. In greenhouse-grown grafts, total water potential (ψT) and relative water content (RWC) of the scions declined rapidly the first 2 weeks. Thereafter, both ψT and RWC were maintained or gradually increased in successful grafts. With scion budbreak, ψT rapidly increased to −1.0 MPa. This increase occurred 1 to 2 weeks after tracheid connections matured, based on dye movement through the graft union. At the same time, the ψT and RWC of unsuccessful grafts declined rapidly. Osmotic potentials (ψw) increased 3 weeks prior to budbreak in successful grafts. However, ψπ declined in unsuccessful grafts more rapidly than ψT, resulting in increased calculated turgor pressures with graft failure. Lath house-grown grafts had higher scion ψT and higher graft success than those in the greenhouse, but required more time for union development. Based on this data and previous work, an hypothesis relating changes in ψT, maturation of connecting tracheids, and scion budbreak to graft success or failure is presented.
S.M. Scheiber, R.C. Beeson Jr, J. Chen, Q. Wang, and B. Pearson
Solenostemon scutellarioides (coleus) were grown in drainage lysimeters in concurrent experiments to evaluate effects of irrigation quantity and frequency on growth responses, leaf gas exchange, and nitrate leaching. Lysimeters in Expt. 1 were irrigated either with 13 mm daily or 13 mm every other day. Daily irrigation increased mean leachate and doubled nitrate leached compared with every other day (22.9 kg·ha−1 N versus 10.8 kg·ha−1 N, respectively). In Expt. 2, lysimeters were irrigated every 2 days with 13 mm or every 3 days with 18 mm such that total depth applied was equivalent. Irrigation frequency had no effect on irrigation quantity or nitrate leached. In these experiments, assimilation rates, stomatal conductance, and transpiration rates were influenced by day since irrigation with values lower on days without irrigation. However, neither irrigation quantity nor frequency affected final shoot dry weight, root dry weight, height or growth indices (P > 0.05).