This research, started during the 1980s, led to development of SRM-Red, a selective reflecting mulch that has been available commercially since 1996.

His best-known work involved tomatoes and strawberries. In research done with Clemson University, he and ARS soil scientist Patrick G. Hunt found that tomato plants grown over red mulch yielded about 20 percent more fruit than those grown over standard black mulch. He later found that strawberries grown over red mulch smelled better, tasted sweeter, and yielded more than those grown over black mulch.

This unique perspective led to studies in which Kasperbauer—who recently retired from ARS ' Coastal Plains Soil, Water, and Plant Research Center at Florence, South Carolina—headed development of colored plastic-sheeting-type mulches that increase food and crop plants' yield and quality.

Plant physiologist Michael J. Kasperbauer made a career of "seeing" light the way plants do: in wavelengths, some of which cannot be detected by the human eye.

Beta carotene, a provitamin found in plants and their pigments, is a benign source of vitamin A and is an antioxidant with possible anticarcinogenic properties. Vitamin C helps maintain capillaries, bones, and teeth; assists in iron absorption; and is vital in the formation of a protein that gives structure to bones, cartilage, muscle, and blood vessels.

They found that concentrations of nutrients and compounds such as beta carotene and vitamin C in the roots of food crops could be modified by reflecting the right waves of color onto the plants' leaves. This was demonstrated in carrot plants. The carrots were grown in trickle-irrigated field plots mulched with plastic sheets colored a shade of yellow that reflected low levels of blue light coupled with high amounts of red, far-red (FR), and photosynthetic light.

Recently, colored-mulch studies have focused on how different wavelengths of light affect roots, stems, leaves, fruit, and seeds of many other food and crop plants. Kasperbauer and colleagues found that some colors enhanced plant products' flavor, aroma, and nutrient content.

Kasperbauer also headed studies with basil, which revealed that the amounts of blue, red, and FR light reflected onto developing leaves affected their size, aroma, and concentration of soluble phenolics. Phenolics are naturally occurring compounds that include tannins and pigments. They induce—among other properties—color, some flavors and odors, and antioxidant activity.

He concluded that the FR light reflected to developing cotton bolls can penetrate the boll walls to reach the developing fiber within and influence elongation.

"We set out to see whether cotton fibers would be as responsive to extra far-red light as the elongating cells in seedling stems are," says Kasperbauer. "We found that the difference in fiber length was influenced more by the higher FR-to-red ratio reaching the developing bolls than by increased photosynthetic light."



Technician Woodrow Sanders

(left) and plant physiologist

Michael Kasperbauer test colored

plastic mulches in 1991 as

yield boosters for tomatoes

and other crops.

(K4101-8)