Fred T. Davies
Fred T. Davies
Sven E. Svenson and Fred T. Davies Jr.
Variation in tissue elemental concentration in apical stem cuttings of `Lilo' and `V-10 Amy' poinsettia (Euphorbia pulcherrima Willd. ex. Klotzch) were studied during the initiation and development of adventitious roots. Changes in selected macro- and micro-element concentrations coincided with root initiation (i.e., Fe, Cu, and Mo accumulated in the basal portions of stem cuttings during early root initiation before root primordia elongation); P, K, Ca, and Mg concentrations declined. During root primordia elongation and root emergence, Fe, Cu, and Mo and Mg, Mn, B, and Zn concentrations continued to increase at the cutting bases, but P and K concentrations remained low compared to when cuttings were initially inserted in the propagation medium. When all cutting of both cultivars had rooted, foliar N, Fe, and Mo concentrations declined, but Cu increased compared to when cuttings were initially propagated.
Lop Phavaphutanon and Fred T. Davies Jr.
Growth and nutrient content of neem tree seedlings (Azadirachta indica A. Juss) were studied in response to the mycorrhial fungi Glomus intraradices Schenck & Smith and Long Ashton Nutrient Solution (LANS) modified to supply phosphorus (P) at 0.65 and 1.30 mM P. Three months after inoculation, an extensive mycorrhizal colonization was observed in mycorrhizal plants at both P levels. Shoot growth of mycorrhizal plants was similar at both P levels while the growth of nonmycorrhizal plants increased with increasing P supply. Mycorrhizal plants had greater leaf area, shoot dry weight and root to shoot ratio than nonmycorrhizal plants at the same P level. The length of nonsuberized roots increased with increasing P supply regardless of mycorrhizal colonization while the length of suberized roots was significantly increased by mycorrhiza. Mycorrhiza altered dry mass partitioning to root systems resulting in greater length and dry weight of suberized roots in mycorrhizal plants. Mycorrhiza also improved nitrogen, phosphorus, calcium and sulfur uptake but did not affect micronutrient uptake, except for enhancing boron.
Fred S. Davies and Leah E. Willis
Sharon A. Duray and Fred T. Davies Jr.
A laboratory exercise is outlined and discussed for seed priming, or osmoconditioning. The exercise was developed using an easily constructed and inexpensive seed-priming system. A variety of horticultural seeds can be used to give students experience and exposure to some of the benefits of seed priming. Seed germination data usually can be obtained within 6 to 8 days, depending on the species used. The laboratory may be modified to stress various features of seed priming, including priming agents, optimal concentrations, and ranges of germination temperatures.
Chuanjiu He, Fred T. Davies, and Ronald Lacey
There are advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or space-flight environments. Elevated levels of the plant hormone ethylene occur in enclosed crop production systems and in space-flight environments—leading to adverse plant growth and sterility. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa L. cv. Buttercrunch). Growth was comparable in lettuce grown under low (25 kPa) and ambient (101 kPa) total gas pressures. However, tip burn occurred under ambient, but not low pressure—in part because of adverse ethylene levels. Under ambient pressure, there were higher CO2 assimilation rates and dark respiration rates (higher night consumption of metabolites) compared to low pressure. This could lead to greater growth (biomass production) of low pressure plants during longer crop production cycles.
Sharon A. Duray and Fred T. Davies Jr.
Plant propagation instructors are challenged to develop laboratory exercises that demonstrate the theoretical aspects of seed germination. Seed priming or osmoconditioning is a relatively new technigue that has been shown to improve seed performance in horticultural crops. An esaily constructed seed priming system was designed using a pair of 2-liter glass jars, 2 aquarium pumps and air tubing. Eight sets of 40 seeds were each wrapped in coffee filters and laced in aerated treatment solutions consisting of 50 mmole K H2P O4 or an untreated control of distilled water. All seeds were treated or 0, 1, 3 or 5 days. Upon completion, seeds were rinsed, dried and placed into petri dishes containing moist filter paper to observe germination. A good test species for this exercise is Vinca rosea which typically has a poor germination percentage and rate. Seeds primed for 3 and 5 days significantly enhanced both germination percentage and rate in Vinca.
Yong Cheong Koh and Fred T. Davies Jr.
The leaves of vegetative stolons of greenhouse grown Cryptanthus `Marian Oppenheimer' (wide leaf clone) were cultured in modified MS media to induce adventitious shoot formation via callus formation. The best callus induction medium was basal MS medium with 10 μM NAA, IBA and BA. Pure green (843), maroon (3), striped (2) and albino plantlets were obtained. Most of the albino plantlets were stunted, tightly clumped together and impossible to score. The medium which produced the highest average number of non-albino plantlets was basal MS medium with 0.3 μM NAA, IBA and BA All non-albino plantlets were rooted in MS medium with 5.4 μM NAA and transplanted ex vitro with a survival rate of 96.7%. The maroon plantlets became green two weeks after transplanting. Histological studies revealed that C. `Marian Oppenheimer' (wide leaf clone) has two tunicas (L1 and L2) and a corpus (L3). Callus on the leaf explant arose mainly from the L2 and L3. Apparently C. `Marian Oppenheimer' (wide leaf clone) is a GWG periclinal chimera.
Sven E. Svenson, Fred T. Davies Jr., and Calvin E. Meier
The influence of ectomycorrhizae on drought acclimation was studied in an open-pollinated family of loblolly pine (Pinus taeda L.). Seedlings inoculated with Pisolithus tinctorius (Pers.) Coker and Couch (Pt) maintained a higher shoot relative growth rate under high and low soil moisture regimes. However, fascicle area, shoot and root mass, and fascicle nutrient elemental content were similar for seedlings inoculated with Pt and noninoculated seedlings. Seedlings under low soil moisture were drought-acclimated by five 11-day drought cycles. During peak water deficit (cycle 6), drought-acclimated, Pt-inoculated seedlings had the lowest predawn fascicle water potential (ψ pd), conserved water with lowest bulk fascicle diffusive conductance (g), and maintained low g and transpiration (E) during recovery (cycle 6). Enhanced drought acclimation of Pt-inoculated seedlings was independent of plant size and fascicle nutrient content.