Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/11/2003
Publication Date: 2/1/2004
Citation: Kasperbauer, M.J., Loughrin, J.H. 2004. Morphogenic light reflected to developing cotton leaves affects insect-attracting terpene concentrations. Crop Science. 44:198-203. Interpretive Summary: Cotton leaves have a characteristic odor that is attractive to insect pests. Our objective was to determine if color of light reflected to cotton leaves during development could influence the concentration of compounds contributing to cotton leaf odor. The plants were grown in drip-irrigated field plots over plastic soil covers that reflected different amounts of photosynthetic light as well as various ratios of blue, red, and far-red light to the developing leaves. The rationale was that color and intensity of light can act through the plants' natural growth regulating system to influence leaf size and chemical composition in a number of crop plants. Cotton leaves that were exposed to a low amount of reflected blue and a far-red to red ratio higher than that of incoming sunlight were thinner than leaves exposed to high amounts of reflected blue and photosynthetic light during development. However, increasing the far-red to red ratio while decreasing the amount of blue reflected to developing cotton leaves increased the leaf content of insect attractants. The results of this study have implications in cotton production practices or pest management programs that can alter the far-red and red light environment of developing leaves.
Technical Abstract: Cotton (Gossypium hirsutum L.) leaves accumulate volatile terpenes that have been implicated in the attraction of both insect pests and the arthropods which prey upon them. Our objective was to determine if altering the light environment of developing cotton leaves could affect the accumulation of these attractants. Plants were grown in drip-irrigated plots over colored polyethylene soil covers that reflected various combinations and intensities of red (R), far-red (FR), blue (BL) and photosynthetic photon flux (PPF). Individual terpenes were quantified by gas chromatography and identified by gas chromatography/mass spectroscopy. Leaves exposed to a low amount of reflected blue and a FR/R ratio higher than that of incoming sunlight were thinner than leaves exposed to high amounts of reflected BL and PPF during development. Increasing the FR/R ratio while decreasing the amount of BL reflected to developing cotton leaves increased the leaf content of insect-attracting terpenes such as alpha-pinene and beta-pinene on both leaf area and fresh weight bases. We conclude that altering the color of light reflected to developing cotton leaves can affect leaf content of insect attractants.