Milkwort jewelflower facts for kids

Streptanthus polygaloides is a cool flowering plant from the mustard family. People often call it the milkwort jewelflower. You can only find this plant in a special area: the Sierra Nevada foothills in California. It loves to grow in forests and chaparral areas, especially where the soil is serpentine.

Meet the Milkwort Jewelflower

The milkwort jewelflower can look quite different from one plant to another. Generally, it's an annual herb. This means it grows, flowers, and dies within one year. Its stem can be very short, less than 10 centimeters, or grow almost a meter tall! The stem is usually smooth and sometimes feels waxy.

When the plant is young, its leaves near the ground are divided into thin parts. These leaves have small stems called petioles. Higher up on the main stem, the leaves are simple and long, up to 10 centimeters. These upper leaves don't have petioles.

The flowers grow along the top part of the stem. Each flower has a folded, hood-like outer part called a calyx. These sepals are often greenish-yellow to purple. White petals with brown veins peek out from the tip of the flower. After the flower blooms, it forms a fruit. This fruit is a smooth, straight, and flat pod called a silique, which can be up to 5 centimeters long.

A Plant That Loves Nickel!

The Streptanthus polygaloides plant is super special because it's a hyperaccumulator of nickel. What does that mean? It means the plant can take in and store huge amounts of nickel from the soil. To be a hyperaccumulator, a plant needs to have at least 1,000 µg of nickel per gram of its dry weight. This jewelflower averages between 2,430 and 18,600 µg/g! That's a lot of nickel!

This amazing ability helps protect the plant from many dangers. For example, the high nickel levels act like a shield against tiny enemies called pathogens. These include plant diseases like powdery mildew (Erysiphe polygoni), harmful bacteria like Xanthomonas campestris, and fungi such as Alternaria brassicola.

The nickel also helps defend the plant from insects that like to munch on leaves. It can stop creatures like the red-legged grasshopper (Melanoplus femurrubrum) and the moth Evergestis rimosalis. Even root-eating insects, like the cabbage maggot (Delia radicum), are affected. The high nickel levels also protect the plant from the diamondback moth (Plutella xylostella).

However, not all insects are bothered by the nickel. Some insects might eat parts of the plant that have less nickel. Others can handle high-nickel diets, or they eat other plants that are less toxic. In fact, some insects, like the mirid bug Melanotrichus boydi, actually do well on a high-nickel diet! This bug even specializes in eating this plant.

Cleaning Up the Earth with Plants

Because this plant can pull so much nickel from the soil, it's very interesting to scientists. They are looking into using it for something called phytoremediation. This is a fancy word for using plants to clean up soil that's polluted with heavy metals. Imagine plants acting like natural vacuum cleaners for the earth!