Geogenanthus undatus is a newly introduced cultivar of the species G. undatus C. Koch & Linden (seersucker plant), native to Peru (Graf, 1963). The species has a low-growing habit with fleshy, broad, ovate metallic green leaves with parallel bands of pale gray and a characteristic quilted appearance. Geogenanthus undatus C. Koch & Linden ‘Inca’ has darker green leaves and a more compact habit than the species. The seersucker plant holds considerable potential for the interiorscape industry because of its adaptability to low-light environments. Although new species and cultivars are the lifeblood of the ornamental industry, cultural information is not often available at their market introduction. To produce high-quality marketable material, growers need production guidelines for irradiance, temperature, and nutrition regimes, as well as growth control.
The majority of tropical foliage plants are produced for use indoors. Generally, photosynthetic photon flux (PPF) in postharvest settings are suboptimal for plant growth, even for many shade-adapted species. Low PPF can cause foliar chlorosis or necrosis, premature leaf senescence, or internode stretching (Conover and Poole, 1981). These undesirable responses lead to frequent plant replacement, high costs, and consumer dissatisfaction. Growers often acclimate foliage plants to lower PPF during production to improve postharvest performance.
Production PPFs have been shown to affect growth parameters of foliage plants. Species-specific responses have been documented for various growth parameters, such as growth index, dry weight, and root-to-shoot ratio (Conover and Poole, 1981). In addition, production irradiance also affects acclimation. Because the majority of foliage plants are sold for the interiorscape market, postharvest performance is an important aspect of the overall evaluation of a particular species or cultivar for the foliage industry.
Plant growth regulator (PGR) type and concentration have been shown to affect postharvest performance of foliage plants (Cox and Whittington, 1988; Davis, 1987). Timing of application is considered critical to the efficacy of PGRs; they are generally applied early during the production cycle. However, by the time the plant is installed in the postharvest environment, the growth control exerted by the PGR may be less, and thus the PGR effect may not carry over to the interiorscape. If the PGR is applied later during the production cycle, and at an appropriate concentration, the growth control and related enhanced plant quality may be extended into the postharvest period. In the current study, drench applications of α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol) or α-(methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol) were administered to Geogenanthus during the later part of the production cycle. The purpose of a late-production application was to ensure growth control throughout the postharvest period. In addition, we hoped that late application of PGRs would slow down growth during the latter part of production, allowing the plants to accumulate starch instead of allocating carbohydrates to new growth. Starch reserves could be used by the plants after transfer to a low irradiance environment and potentially improve their performance in interiorscapes.
The objectives of this study were to evaluate the effects of PPF and PGR on growth of G. undatus C. Koch & Linden ‘Inca’ during production, to determine whether the responses to the PGRs are similar at different irradiance levels, and, lastly, to evaluate the postharvest performance of G. undatus C. Koch & Linden ‘Inca’ in response to PPF and PGR applied late during the production cycle.
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