NATURAL VIEW:Nature’s smart green factories

The western fence lizards scuttling along my garden wall are often in motion, moving from sun to shade to regulate their internal temperature.

They do this to maximize their hunting success. The warmer they are, the faster they can move. And faster means they catch more insects. They mostly hunt in the leaves of a non-native, ornamental potato vine on the same wall.

Although it can’t move like the lizards, the plant also maximizes its food production through its smart leaves.

Leaves are the energy factories of plants. Through the light-energy trapping of the green pigment chlorophyll, carbon dioxide and water are converted into simple sugars.

It doesn’t stop there. Everything in the plant — the synthesis of all complex organic molecules needed by the plant to grow and flower and set seed — ultimately depends on energy captured by the leaves.

Plants are surprisingly active, solving the problems posed by their environment in elegant and sophisticated ways. But their activity is slower than we fast-living, warm-blooded mammals usually appreciate.

For example, the potato vine grows against a long, light-colored wall. All of the leaves grow on the same long, vining stalk, and they’re just a few yards apart. Yet they look very different.

Leaves growing in the sun are small, narrow and purple. In the shade, the leaves are twice as wide and long, and green.

Young “sun” leaves start out green, but as they spread and sense the intensity of the sunlight, they turn mostly purple. The green of the chlorophyll is masked by a purple pigment, anthocyanin.

Research suggests that anthocyanin acts like sunscreen for the leaves. In winter, responding to less intense sunlight, “sun” leaves lose their purple color and are green.

Why are the “sun” leaves small? Plants native to hot, dry habitats have small leaves that reduce water loss. Apparently this non-native plant, introduced into that same habitat, can limit the size of individual leaves.

Other plants’ smart leaves have distinctly different colors and textures on their two surfaces.

Native Sycamore trees live in the bottoms of our canyons, near streams. A full-grown sycamore pumps hundreds of gallons of water from the ground every day. Its large, maple-like leaves have light-colored, distinctly fuzzy undersides. The fuzz is an intricate tangle of plant hairs that blocks wind from the under surface of the leaf, reducing water loss.

Fuzz also traps water droplets from dew and coastal fog, and insulates the leaves against cold. These functions keep the leaves working longer and better. Finally, leaves can move in response to the sun.

Mugwort is a fairly common native plant of damp places in our wildlands. The top surface of the leaf is green, but the underside is bright white. On hot days, the leaves flip to expose the white side to the sun. This reflects the sunlight and cools the plant.

Manzanita is a handsome shrub of Southern California mountains. Its vertical, dime-shaped leaves are large for a chaparral plant, and actively track the sun. When it’s too hot, the leaves turn so the thin side faces to the sun. Minimizing the surface exposed to the sun cools the leaf.

Lizards also sit broadside to the sun to warm up, then face away to minimize additional heat gain. This lets them regulate their temperature without going under cover and move away from possible prey.

Manzanita and lizards employ the same strategy. You just have to have patience to see how smart the plants are.