Response to alkalinity was evaluated in two hibiscus cultivars, Bimini Breeze and Carolina Breeze, grown in a soilless growing medium and in hydroponic culture. For soilless growing medium, plants were potted in a sphagnum peat–perlite-based substrate and irrigated with solutions containing 0 to 10 mm NaHCO3 for 12 weeks. In hydroponic culture, bare-rooted plants were transferred to a 9-L tray containing a Hoagland's nutrient solution prepared with NaHCO3 at the concentrations previously indicated. In soilless growing medium, shoot dry weight was minimally affected by NaHCO3 concentration for `Bimini Breeze', but `Carolina Breeze' exhibited a significant decrease in shoot mass with increasing NaHCO3 concentration. In hydroponic culture, increasing concentration of NaHCO3 induced a decrease in shoot and root mass in both cultivars, but root mass decrease was more pronounced in `Bimini Breeze'. In soilless growing medium, increasing the concentration of NaHCO3 caused an increase in growing medium pH. The pH increase was less pronounced for `Bimini Breeze' than for `Carolina Breeze', indicating a higher capacity for root zone acidification by `Bimini Breeze'. Newly developed leaves of both cultivars showed increasing chlorosis with increasing NaHCO3 concentration. However, `Bimini Breeze' was more tolerant because, according to regression models, 5.7 mm NaHCO3 would be required to reduce chlorophyll levels by 10%, compared with 2.2 mm for `Carolina Breeze', when grown in soilless medium. Fe reductase activity decreased when `Carolina Breeze' plants were grown in 5 mm NaHCO3. However, in `Bimini Breeze', Fe reductase activity was enhanced. These observations indicate that the increased tolerance of `Bimini Breeze' to increasing alkalinity is the result of enhanced Fe reductase activity and increased acidification of the root zone.
Luis Alonso Valdez-Aguilar and David William Reed
Luis A. Valdez-Aguilar, David William Reed, and John A. Cornell
The effect of Rb+ and Na+ as counter-cations of HCO3 − was evaluated on bean (Phaseolus vulgaris L. cv. Poncho) plants using mixture experiment statistical methodology in a series of experiments set up in a controlled environment chamber. Mixture experiments using three components (Rb+, K+, and Na+) or two components (K+ and Na+) were conducted to delineate the toxicity of HCO3 − versus the counter-cation effect. The quantitative separation of the toxic effects was possible only when the individual stress had an additive effect when combined with the other stress. Potassium mixtures were used as reference for comparison with other mixtures because plants did not respond to K+, probably because it was included at a minimum concentration of 2.5 mm K+ or because it was supplied in the preestablishing solution. Rubidium caused a decrease in shoot dry weight (SDW), but SDW accumulation was even lower when HCO3 − was added to the Rb+ solutions. However, Rb+ was not included in follow-up experiments because the response of plants to Rb+ was very similar to that of Na+. The toxic effect of Na+ caused SDW to decrease at a rate of 3.7% per millimolar increase of Na+. However, the effect of HCO3 − was dependent on its concentration, because at 2.5 mm HCO3 −, the decrease in SDW was 12.7% per millimolar HCO3 −, whereas at 3.75, 5, and 5.65 mm, the decrease was 11.0%, 7.8%, and 10.7% per millimolar HCO3 −, respectively. At 7.5 mm HCO3 −, the decrease in SDW was 4.2% to 8.2% per millimolar increase in HCO3 −, respectively. The decreasing HCO3 − rate may be explained by the nonadditive effect between HCO3 − and Na+ at high alkalinity levels.
Carl E. Niedziela Jr., Christopher D. Mullins, T. David Reed, William H. Swallow, and Eric Eberly
Pre-cooled bulbs of two dutch iris (Iris ×hollandica) cultivars, Ideal and White Wedgewood, were grown and harvested as cut flowers in four production systems in a tobacco (Nicotiana tabacum) transplant greenhouse from late October until late January in two consecutive production years (2000-01 and 2001-02). All production systems (lily crates, lay-flat bags, pots, and float trays) utilized the same commercial peat-vermiculite, tobacco germination substrate. Stems developed more quickly but were shorter and lighter in 2001-02 than 2000-01 due to warmer growing conditions. Stems grown in float trays were shorter and lighter than other treatments in 2000-01 but similar to the others in 2001-02. Stems grown in lay-flat bags flowered earlier with similar or greater stem lengths and fresh weights as the other systems. Stems of `White Wedgewood' were longer and heavier than `Ideal'. In general, `White Wedgewood' provided more consistent production than `Ideal' in both production seasons. An economic analysis in this study concludes that a grower is unlikely to make money growing dutch iris in a tobacco transplant greenhouse using these production systems unless there is a targeted local market.
Michael A. Arnold, R. Daniel Lineberger, Tim D. Davis, David W. Reed, and William J. McKinley
A comprehensive survey of American and Canadian universities that offer masters, doctoral, or both degrees in horticulture resulted in responses from 27 academic units. Units were surveyed regarding types of degrees offered, admissions policies, demographic characteristics of students, financial assistance provided to students, faculty ranks and salaries, and metrics by which the programs were evaluated by university administration. About 80% of the programs resided in 1862 Morrill Act land-grant institutions (LG) with the remainder housed in other non-land-grant institutions (NLG). Thirty-eight percent of reporting LG programs existed as stand-alone horticulture departments, whereas horticulture programs were combined with other disciplines in the remainder. Admissions criteria were most consistent among LG programs. Participation in distance education programs was low, but growing. Financial support of graduate students was more common in LG programs. Most schools offered some sort of tuition reduction to those students on assistantships/fellowships and offered health insurance options. Payment of fees was rare and the level of stipends provided varied substantially among programs. International student enrollment was greatest at LG programs and had remained steady in recent years. Gender equity was present among graduate students, with nearly equal male and female enrollment. Most graduate students at both LG (63.6%) and NLG (75.0%) programs were non-Hispanic White; although overall minority enrollment had increased but was still not similar in distribution to that of the general U.S. population. Professors (46.7%) and Associate Professors (28.3%) dominated the faculty ranks while Assistant Professors (19.3%) and lecturers/instructors (5.7%) constituted a much smaller portion of the faculty. Faculty salaries varied tremendously among institutions, especially for senior faculty. Female and ethnic minorities were underrepresented in faculty ranks compared with the general U.S. population. Aside from total graduate program enrollment, the relative importance of various evaluation metrics for programs was highly variable among institutions. Data discussed herein should be useful to universities with horticulture graduate programs for peer institution comparisons during program assessments, accreditation reviews, or for strategic planning purposes.