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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #58429
Title: MULCH SURFACE COLOR AFFECTS ACCUMULATION OF EPICUTICULAR WAX ON DEVELOPING LEAVES

Author
item Kasperbauer, Michael
item WILKINSON, R - UNIV OF GA

Submitted to: Photochemistry and Photobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plastic mulches over trickle irrigation systems are widely used to conserve water and to control weeds (with less dependence on herbicides) in production of high value food crops. Black mulches are commonly used to warm the soil in spring, and white-surfaced mulches are often used later in the season to avoid overheating the root zone. Recently, it was discovered dthat the quantity and spectral distribution of light reflected from different colored mulches could act through pigment systems such as phytochrome to regulate leaf development, plant growth, and yield. We examined waxes that formed on leaves grown in field plots over white, black, and red mulches. The quantity of reflected blue light was greatest over white and about the same over black versus red mulches; and reflected far-red to red ratios (FR/R) were about the same over white versus black and higher over red. Plants grown over white mulches developed significantly more total wax on both leaf area and leaf weight bases. The total quantities of waxes were the same on leaves that developed over black and red mulches. However, when individual lipid classes were expressed as percentages of the totals, esters dominated over white and black, while secondary free fatty alcohols dominated over red mulches. We conclude that the total wax concentration on leaves of field-grown plants was driven by quantity of blue light, and the concentration of individual components was influenced by the FR/R ratio.

Technical Abstract: Leaf waxes are important to plant growth because they impede water loss and may influence entry of light. Plant growth and leaf wax quantity and composition were studied in trickle-irrigated field plots covered with white, black, or red plastic mulches. The quantity of reflected blue light (BL) was greatest over white and about the same over black versus red mulches; and reflected far-red to red ratios (FR/R) were about the same over white versus black and higher over red. The greatest quantity of total epicuticular wax developed on leaves of plants grown over white mulch (44.3 mg/dm2) while plants grown over black and red mulches had 22.9 and 22.7 mg/dm2, respectively. When individual lipid classes were expressed as percentages of the totals, esters dominated over white and black mulches while secondary free fatty alcohols dominated over red. Comparison of wax components of leaves grown over black versus red provided a comparison of FR/R effects. The higher ester content of epicuticular wax on plants grow over black versus red was almost exactly equalled by increased contents of free fatty alcohols and free fatty acids in the epicuticular wax of plants grown over red mulch. We conclude that the total wax concentration on leaves of field-grown plants was driven by quantity of BL, and the concentration of individual components was influenced by the FR/R ratio.