Managing Calcium

A new understanding of how plants manage their internal calcium levels could lead to avoiding damage from acid rain. The pollutant disrupts calcium balance in plants by leaching significant amounts of the mineral from leaves as well as the agricultural and forest soils the plants live in.

To grow, a plant needs a reliable supply of calcium, which enters the plant through water that the roots take in from surrounding soil. As water circulates through a plant, dissolved calcium gets shuttled where it is needed to give the plant's cells their structural rigidity. But calcium supplies coming into the plant cycle up and down over the course of the day and drop to a minimum at night.

Plants use molecular sensors and flows of chemical messengers to detect and regulate the storage and distribution of vital nutrients such as water and calcium. To track the calcium sensors in the laboratory plant Arabidopsis, researchers used molecules originally found in jellyfish that emit light in the presence of calcium. To deduce the calcium sensor's role, they also introduced an altered version of the sensor protein that abolishes the sensor's effects.

According to researchers, the sensors try to detect how much calcium there is and coordinate that level with growth and development.

Acid rain robs soil of much of its calcium. Although enough is still left for plants to live on, the sensors may misinterpret "less" as "too little" in those plants and unnecessarily signal for growth shutdowns.

"Some soils have lost as much as 75 percent of their calcium during the past century," said Zhen-Ming Pei, a Duke University biologist who led the study. "One way to respond is to add new calcium to the soil. But we can't do that everywhere that it's needed, and it is also expensive. Perhaps a plant's calcium sensors could instead be tricked into interpreting "less" as "still enough" and keep building new cell walls."

---LiveScience Staff

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