Description of the light environment used in photomorphogenic research varies greatly among research teams. The environment is often described as the ratio of red (R) to far-red (FR) light, particulary when involvement of the phytochrome system is suspected. There is disagreement in the appropriate center and range of values for each ratio component. Often the center for R is reported as 660 nm. However, in chlorophyll-containing tissue 645 nm may be more appropriate because of the absorption of chlorophyll at 660. Band widths around a selected peak also vary. The widths generally are 10 or 100 nm. Comparison of experiments that describe different peaks or ranges is difficult. Much of the variation in description results from the behavior of phytochrome. Phytochrome has absorption and action spectral peaks, however wavelengths that cause absorption and/or action to a lesser extent may extend more than 50 nm from the peak. Integration formulas such as Pfr/P consider the effects of all wavelengths. However, even the integration formulas do not explain all photomorphogenic responses. A description of the entire photomorphogenic spectrum may be the most appropriate means of communication.
Robert Pollock, Margaret J. McMahon, and John W. Kelly
Jeffrey Adelberg, Robert Pollock, Nihal Rajapakse, and Roy Young
Two varieties of Cattleya orchids (C. Loddigessi `Elen' × C. Loddigessi Alba `Extra' and Brassolaeliocattleya. Mem. `Helen Brown' Sweet Afton) were micropropagated in sealed, three-dimensional polypropylene vessels with microporous, semi-permeable membrane films to allow diffusion of water, dissolved nutrients, and gas to plant material inside the vessels. During tissue culture on sugar-containing media, chance contaminants were eliminated on the vessels outer surface using 5% bleach solution. Proper decontamination treatment did not effect carbohydrate content or subsequent growth of tissues contained within the vessels. Plantlets remaining in membrane vessels were shipped (7 days at 14–30°C) from Japan to the United States in the dark in a plastic tray and arrived without changes in fresh or dry weight of whole plantlets. However, shoot dry weight did increase significantly. Sucrose, glucose, and fructose reserves established on sugar-containing media were greater in root than shoot tissue and were largely expended during shipping concurrent with increased shoot dry weight. It is likely carbohydrate catabolism provided energy for these CAM plantlets to continue carbon fixation, resulting in positive net carbon assimilation in the dark shipping environment. Changes in starch concentrations during shipping were not significant. Plantlets grew photoautotrophically in hydroponic culture in the greenhouse, following transport in the same sealed membrane vessels. Carbohydrate concentration of plantlets following hydroponic culture was not significantly different than after the shipping process. Sealed-membrane vessels for micropropagation, decontamination, shipping and greenhouse growth were useful for culture of Cattleya to facilitate scale-up of materials handling and international commerce of tissue-cultured plants.
Nihal C. Rajapakse, Robert K. Pollock, Margaret J. McMahon, John W. Kelly, and Roy E. Young
Experiments were conducted to correlate the response of chrysanthemum [Dendrathema ×grandiflorum (Ramat.) Kitamura] plants to light environment based on various quantitative light quality parameters by growing plants under 6% or 40% CuSO4 and water spectral filters. Using a narrow band width (R = 655-665 and FR = 725-735 nm) or a broad band width (R = 600-700 and FR = 700-800 nm) for R: FR ratio calculation, 6% CuSO4 filter transmitted light with a higher R: FR ratio than 40% CuSO4 or water filters. Light transmitted through 40% CuSO4 and water filters had similar narrow band R: FR ratios (≈1.2), but the broad band R: FR ratio (2.0) of 40% CuSO4 filter was higher than that of water filters. The estimated phytochrome photoequilibrium (ϕ) value varied considerably with the photochemical properties of phytochrome used for estimations. Final height and internode length of plants grown in 6% or 40% CuSO4 chambers was ≈30% less than of plants in corresponding control chambers. Leaf and stem dry weights were reduced by light transmitted through CuSO4 filters. The results suggest that broad band R: FR ratio correlated more closely to above plant responses than the narrow band R: FR ratio. Blue (B): R and B: FR ratios (not absolute amount of blue wavelengths) correlated well with plant response, suggesting that involvement of blue light should not be ignored in expressing plant response to light transmitted through CuSO4 filters. At present, the presentation of complete spectral data would be the most useful in explaining plant response to light environment.
Elsa Sánchez, Thomas Butzler, Lee Stivers, Robert Pollock, Timothy Elkner, Steven Bogash, and William Lamont
Recent hypothetical modeling suggests that increasing commercial broccoli (Brassica oleracea var. italica) acreage in the eastern United States has the potential to notably reduce the costs of transportation within the broccoli supply chain. In this region, increasing broccoli acreage will require production improvements. Here, research was conducted to determine the best yielding commercially available cultivars for broccoli production. Eighteen to 19 cultivars of broccoli were evaluated in spring and fall evaluations using diverse production systems during 2014–15 in three locations across Pennsylvania. Data collected included production, yield, and quality attributes. Most interactions between site, year, and cultivar were significant suggesting that environmental conditions influence broccoli yield, quality, and concentration of harvest. Overall, the cultivars evaluated were not different from, Imperial, the standard used, for marketable yield, head diameter, and concentration of harvest within a site year. Blue Wind was consistently the first cultivar harvested, and Avenger and Emerald Jewel the last overall site years and growing seasons. These three cultivars may be good options for extending the growing season.
Dennis R. Decoteau, Heather A. Hatt, John W. Kelly, Margaret J. Mcmahon, Nihal Rajapakse, Roy E. Young, and Robert K. Pollock
Thomas M. Butzler, Elsa S. Sánchez, Steven M. Bogash, Timothy E. Elkner, William J. Lamont Jr., Robert Pollock, and Lee J. Stivers
To provide growers with regional and statewide recommendations, 23 cultivars of bicolor and white synergistic sweet corn (Zea mays) were evaluated in southwestern, central, and southeastern Pennsylvania. ‘Temptation’ was the standard. Despite differing production practices used in all locations, all cultivars were not different or produced more marketable primary ears compared with Temptation. Paydirt was the only cultivar to produce lower marketable yields by weight than Temptation in 2 site years or more. However, ‘Paydirt’ has an early maturity, which improves its acceptability. Very few ears were unmarketable. In terms of ear size, measured as diameter and length, overall all cultivars were not different from Temptation. ‘Temptation’ is early maturing and ear size was expected to be smaller than later maturing cultivars. This was not observed. Ease of hand harvesting was determined by measuring two factors: distance from the base of the primary ear to the soil line and ease of picking (1–5 rating scale where 1 = difficult and 5 = easy). The closer the primary ear was to the soil line was thought to be more difficult to harvest. ‘Synergy’, ‘Espresso’, ‘Kristine’, and ‘Paydirt’ ears were lower than ‘Temptation’ on the culm in 2 site years or more. ‘Whiteout’, ‘Synergy’, and ‘Mattapoisett’ were rated as more difficult to pick than ‘Temptation’ in 2 site years or more. Distance from the soil line to the primary ear and picking ease ratings were not observed to be closely related to each other and a combination of these and other factors may more accurately reflect the ease of hand harvesting. Overall, growers in our region have access to a lot of synergistic sweet corn cultivars with acceptable yield, quality, and ease of hand harvesting characteristics giving them a wide range of options.