Racemes of Big Bend bluebonnet (Lupinus havardii Wats.), a winter annual native to far west Texas with attractive blue flowers, are currently being produced commercially as a specialty cut-flower crop. Our studies indicated that the key determinants of postharvest longevity and performance are flower abscission and flower senescence, both of which can be influenced by ethylene. Therefore, this study was undertaken to evaluate the role of some ethylene biosynthesis inhibitors (aminooxy acetic acid = AOA; cobalt = CO++; salicylic acid = SA) and an ethylene action inhibitor (silver thiosulfate = STS) on flower abscission and flower senescence of bluebonnet racemes. Depending on the concentration used (10 μM - 1 mM), AOA and CO++ exhibited variable effects on flower abscission, flower senescence and vaselife. SA (10-100 μM) slightly delayed senescence but did not affect abscission, while higher levels of SA (500 μM - 2 mM) slightly promoted abscission and also significantly enhanced the senescence of flowers on cut racemes. The effects of SA were found to be pH-dependent. However, STS nearly eliminated flower abscission and enhanced vaselife. The results also demonstrated that the abscission of bluebonnet flowers, in particular, is highly sensitive to ethylene.
W.A. Mackay, D. Sankhla, T.D Davis, and N. Sankhla
D. Sankhla, T.D. Davis, N. Sankhla, and A. Upadhyaya
This report describes an efficient in vitro regeneration protocol for H. patens (firebush), a heat-tolerant ornamental shrub native to tropical and subtropical America. Shoot cultures were initially established using shoot tips placed on MS-revised medium containing 2.3 μM 2,4-D, 2.3 μM kinetin, and 0.25% polyvinylpyrrolidone. Other types of explants (nodal and internodal segments, leaf pieces, floral buds) did not regenerate shoots when placed on this medium. Two-month-old plantlets derived from the shoot tips were subcultured on MS medium supplemented with 0.5 μM thidiazuron (TDZ), and within 3 to 4 weeks, some callus was produced at the root–shoot junction. When this callus, with a small portion of the root and shoots, was placed on MS medium with 0.05 μM TDZ and 0.01 μM ABA, prolific shoot formation occurred within 3 to 4 weeks followed by root formation. By regular subculturing every 5 to 6 weeks, hundreds of plantlets have been obtained over the past 3 years with no apparent decline in regeneration potential. Addition of activated charcoal (0.5%) to the culture medium has greatly improved growth of the plantlets.
E.C. Boehm, T.D. Davis, and J.O. Kuti
Relative water usage of four species of container-grown woody ornamental shrubs (Buxus japonica (Japenese boxwood), Leucophyllum frutescens (Texas sage), Ligustrum japonica (ligustrum) and Pittosporum tobira wheeleri (dwarf) pittosporurm)), normally used for home landscaping in south Texas, were evaluated by comparing water consumption and frequency of watering with growth rates and horticultural quality after six months growth in containers. Growth rates were determined by the difference in plant height and leaf area from the control unwatered plants and were used to characterize the suitability of ornamental shrubs for xeric landscapes. While frequency of watering had no significant effects on plant height, only ligustrum and dwarf pittosporum plants watered on weekly basis showed positive change in leaf area. There was considerable leaf regrowth in Texas sage plants after initial leaf loss. Of all the shrubs tested, dwarf pittosporum plants watered biweekly used less water to maintain their horticultural quality.
T.E. Morelock, J.L. Bowers, D.R. Davis, and D.R. Motes
Southernpeas are an important crop to Arkansas processors, market gardeners and home gardeners. While the bulk of the acreage produced in the state is pinkeye purple hull types, there is a demand for other horticultural types. At present some processors consider `White Acre' to be the standard of cream pea quality, but under Arkansas conditions, `White Acre' produces excessive vine growth, is very late to mature and is susceptible to bacterial blight. For these reasons, the Arkansas Agricultural Experiment Station announces the release of `Early Acre'. `Early Acre' has been widely tested under the designation Arkansas 84-154 and produces a very compact bush plant that has seed similar in size and shape to `White Acre', but matures 8-10 days earlier under Arkansas conditions. Although the plant type is well suited to narrow row spacing, `Early Acre' has produced yields similar to `White Acre' when both are planted at conventional row spacings. Samples have been canned by the Dept. of Food Science at the University of Arkansas and the samples have been rated equal to `White Acre' in processed quality. “Early Acre' has exhibited high levels of resistance to bacterial blight in replicated yield trials under field epidemics in both Arkansas and Texas.
A. T. Leonard, D. R. Earhart, J. V. Davis, and V. A. Haby
The increase of the Asian population in Texas has created a demand for specialty vegetables including Chinese cabbage. Chinese cabbage (Brassica rapa L. Pekinensis var. Monument) was grown in a greenhouse to study the main effects of P, K, Ca, Mg, S, Fe, Mn, Zn, B, and Mo on plant growth. A randomized complete block design with 4 replications was used. The elements were incorporated and tested at three rates in soil from the Ap horizon of the Darco series (loamy, siliceous, thermic Grossarenic Paleudult). Treatments consisted of a check, where no nutrients were incorporated, all nutrients incorporated at 1X rates, and all nutrients at 2X rates. Each nutrient was tested individually at the 0 and 2X rates, while the remaining nutrients were held constant at the 1X rate. Analysis of variance indicated plant growth was affected by applications of P, K, S, Zn, B, and Mo. Regression analysis indicated positive growth responses to P, K, S, and Zn, and negative growth responses due to B and Mo applications.
J. V. Davis, D. R. Earhart, A. T. Leonard, and V. A. Haby
The potential for east Texas to produce Brassica that could compete favorably with the import market exists. This study was conducted to establish optimum nitrogen and boron rates for 4 Brassica spp. grown on highly leachable east Texas soil, a Bowie series (fine-loamy, siliceous, thermic, Plinthic Paleudult). Broccoli (Brassica oleracea L. Italica, var. Green Comet), cauliflower (Brassica oleracea L. Botrytis var. White Contessa), Chinese cabbage (Brassica rapa L. Pekinensis var. Monument), and Chinese mustard (Brassica rapa L. Chinensis var. What-A-Joy) were field grown using 5 rates of N (0, 50, 100, 150, and 200 kg·ha-1) interacted with 3 rates of B (0, 1.25 and 2.5 kg·ha-1) in a complete randomized design with 3 reps. Harvested broccoli heads increased average head weight (HW), average head size (HS), and total yield (Y) for each increase of N. Cauliflower HW, HS, and Y increased up to 150 kg N ha-1. B supplementation did not statistically affect HW, HS, and Y of broccoli or cauliflower. Chinese cabbage Y increased up to 150 kg N ha-1 and produced less Y at 200 kg N ha-1 than at 50 kg N ha-1. Chinese mustard Y increased 50% for the 50 (kg·ha-1) N over no added N with additional N producing statistically equal Y. B at 1.25 (kg·ha-1) significantly increased cabbage Y, but had no effect on mustard Y.
D. R. Earhart, V. A. Haby, A. T. Leonard, and J. V. Davis
Soil solarization following previous N application rates of 0, 56, 112, 168 and 224 kg·ha-1 as ammonium nitrate, and one cover crop of-sorghum-sudah (Sorghum bicolor var.) increased yields of turnip foliage (greens) by 3066 kg·ha-1 over the non-solarized treatment. Greater yield was obtained with 56 kg·ha-1 less N with solarization than non-solarization (112 vs 168 kg·ha-1). A blanket N application of 22 kg·ha-1 ameliorated the solarization effect on the 2nd harvest. Solarization had no significant effect on turnip leaf element concentration. Linear and quadratic increases in leaf N occurred as soil N increased. There was also a linear increase in tissue K and Mg due to solarization. No interactive effects were noted. Soil analysis showed salinity (EC) decreased and Ca increased with solarization. An increase in N rates decreased pH, NO3, and Mg, and increased soil salinity and NH4. Solarization had an interactive effect on soil salinity by increasing EC at 0 N and decreasing at 56 to 168 kg N·ha-1.
M.E. Kane, G.L. Davis, T.D. Hoffner, and R.J. Henny
Jeanine M. Davis, D.R. Decoteau, G.D. Hoyt, K.D. Batal, D.C. Sanders, J.T. Garrett, and R.J. Dufault
Tomatoes and beans were grown in rotation for 4 years with three cover crop treatments (bareground, wheat, and crimson clover) and three nitrogen rates (0, 60, and 120 kg N/ha). Over the course of the study, when no additional N was provided, lowest yields of tomatoes and beans were obtained with the wheat cover crop. With the highest N rate, however, there was little difference in yields of beans or tomatoes with any of the cover crop treatments. Considering the benefits associated with the use of cover crops, it is encouraging to see that with proper N amendment, yields obtained with cover crop systems can be comparable to conventional bareground systems.
D.C. Sanders, G.D. Hoyt, J.C. Gilsanz, J.M. Davis, J.T. Garrett, D.R. Decoteau, R.J. Dufault, and K.D. Batal
`Jewel' sweetpotato was no-till planted into crimson clover, wheat, or winter fallow. Then N was applied at 0, 60, or 120 kg·ha–1 in three equal applications to a sandy loam soil. Each fall the cover crop and production crop residue were plowed into the soil, beds were formed, and cover crops were planted. Plant growth of sweetpotato and cover crops increased with N rate. For the first 2 years crimson clover did not provide enough N (90 kg·ha–1) to compensate for the need for inorganic N. By year 3, crimson clover did provide sufficient N to produce yields sufficient to compensate for crop production and organic matter decomposition. Soil samples were taken to a depth of 1 m at the time of planting of the cover crop and production crop. Cover crops retained the N and reduced N movement into the subsoil.