Lettuce (Lactuca sativa L. cv. Summer-green) plug transplants were grown for 3 weeks under 16 combinations of four levels (100, 150, 200, and 300 μmol·m-2·s-1) of photosynthetic photon flux (PPF), two photoperiods (16 and 24 h), and two levels of CO2 (400 and 800 μmol·mol-1) in growth chambers maintained at an air temperature of 20 ±2 °C. As PPF increased, dry mass (DM), percent DM, and leaf number increased, while ratio of shoot to root dry mass (S/R), ratio of leaf length to leaf width (LL/LW), specific leaf area, and hypocotyl length decreased. At the same PPF, DM was increased by 25% to 100% and 10% to 100% with extended photoperiod and elevated CO2 concentration, respectively. Dry mass, percent DM, and leaf number increased linearly with daily light integral (DLI, the product of PPF and photoperiod), while S/R, specific leaf area, LL/LW and hypocotyl length decreased as DLI increased under each CO2 concentration. Hypocotyl length was influenced by PPF and photoperiod, but not by CO2 concentration. Leaf morphology, which can be reflected by LL/LW, was substantially influenced by PPF at 100 to 200 μmol·m-2·s-1, but not at 200 to 300 μmol·m-2·s-1. At the same DLI, the longer photoperiod promoted growth under the low CO2 concentration, but not under the high CO2 concentration. Longer photoperiod and/or higher CO2 concentration compensated for a low PPF.
Yoshiaki Kitaya, Genhua Niu, Toyoki Kozai, and Maki Ohashi
Dewayne L. Ingram, Charles R. Hall, and Joshua Knight
operational variables and for variable costs in two of those 15 operations in the no. 3 container production phase. Assessed from cutting-to-gate, a 10% increase in the GWP of the container, transplant/transplanting, and irrigation would have more than a 2
Roberta J. Tolan and James E. Klett
Patmore green ash (Fraxinus pennsylvanica `Patmore'), Bur oak (Quercus macrocarpa), and Austrian pine (Pinus nigra), were used to measure growth differences of trees produced using three different production methods: balled and burlapped, plastic container, and fabric container (grow bag). Two irrigation frequencies were also established. A pressure chamber was used to measure the xylem water potential and to determine tree water requirements and irrigation scheduling. The balled and burlapped trees showed the least new growth of the three production methods across all three tree types. The production method showing the most new growth varied by genera. Plastic container ash trees grew considerably more than the fabric container ash; fabric container oak grew significantly more than plastic container oak; and there was no measurable difference between the new growth of the plastic container and fabric container pines. The fabric container transplants required more frequent irrigation than did the balled and burlapped trees. Under high temperature and drought conditions, fabric container trees showed stress earlier than did the balled and burlapped or plastic container trees.
Carlos A. Parera and Daniel J. Cantliffe
`Verina' leek (AIlium porrum L.) seed germination is normally reduced at temperatures > 25C. Leek seeds were primed in aerated solutions (1.5 MPa, 10 days at 15C) of d-mannitol (mannitol), polyethylene glycol-8000 (PEG), KNO, and a nonaerated solution of PEG-8000 (PEG). At high temperatures mannitol, PEG, and PEG significantly enhanced germination percentage relative to KNO, or the control. At constant 30C, the mannitol, PEG, and PEG treatments increased final germination almost 10 times and the coefficient of velocity (COV) was improved compared to KNO, and the control. 10 growth chambers with alternating day/night temperatures (38 to 28C or 32 to 22C, 10 to 14 hours, respectively), primed seeds had significantly higher emergence and a larger COV than the control. In a greenhouse study under good conditions for germination, total emergence of primed and nonprimed seeds was similar; however, mannitol, PEG, and PEG led to a significantly higher COV than the control or KNO, treatments. These controlled-environment results demonstrate that priming leek seeds via mannitol, PEG, and PEG may promote early emergence at high temperature and improve stand uniformity for container transplant production.
Donita L. Bryan, Michael A. Arnold, Astrid Volder, W. Todd Watson, Leonardo Lombardini, John J. Sloan, Luis A. Valdez-Aguilar, and Andrew D. Cartmill
at 10 cm above grade. The correlation between initial height and final height was unaffected by container transplanting practices or field transplanting ( Fig. 4 ). Table 2. Significance of planting depth on growth of lacebark elm ( Ulmus
smallest in 2-inch containers, and intermediate in 6-inch and 8-inch-tall containers. TRANSPLANT PRODUCTION REGION INFLUENCES EARLY SEASON STRAWBERRY PRODUCTION IN FLORIDA Geographical location of strawberry transplant production has