Páez-Delgado, Dewell D.

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    Comparative study using open-top growth chambers and ambient plots to evaluate the effect of chamber microclimate on sugarcane (Saccharum spontaneum Cv. US-67-22-2)
    (2007) Páez-Delgado, Dewell D.; Pérez-Alegría, Luis R.; College of Agricultural Sciences; de la Torre, Winston; Román Paoli, Elvin; Department of Crops and Agro-Environmental Sciences; Harmsen, Eric W.
    Cylindrical open-top chambers are experimental facilities that have been widely used to study the effect of CO2 and toxic gases on plants. The difference in the chamber environment constitutes unintentional effects of experiments using open-top field chambers. The objective of this research was to study the effect of open-top chambers (CH) on the physiology of sugarcane variety US-67-22-2 in comparison to ambient air plots (AA). The chambers were 4.66 m diameter and 3.6 m high with 0.02 cm (8mil) polyvinyl chloride film covering an aluminum frame. The experiment was conducted at Lajas Agricultural Experimental Substation in Lajas, Puerto Rico. The environment of the open-top chambers was found to differ from the ambient air plots. Photosynthetically active radiation was reduced by 18 to 20% inside the chambers due to the chamber film and aluminum frame. Mean air temperatures inside the open-top chambers were on average 1.3 oC higher than ambient plots. Short term differences up to 2.5 oC were also observed on sunny days. CO2 concentrations were virtually the same for both treatments. The environmental changes were shown to cause little differences in plant development. Significant differences where found in plant height (P < 0.018) and in the number of leaves on the main stem (P < 0.04) of the sugarcane. The plant height in the chambers was taller by 34% from the ambient plots. No significant differences were observed in the number of tillers (P < 0.15), total leaf area (P < 0.06), leaf photosynthesis (P < 0.10) and leaf chlorophyll content (P < 0.09). No significant differences in any of the fresh and dry weight of plant parts were found between the CH and AA plots, although average weights were higher in the AA plots. Although there is some modification of the plant environment, the chambers provide a suitable environment during the growing season to be use in CO2 studies. Mathematical models were used to study the agronomic variables (height, leaf area, number of leaves, and number of tillers). The models with the best adjustments curve in relation to days after planting and degree day were the sigmoid and quadratic for the respective variables.