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It ain't over 'til the fat cell sings

Q: In the absence of clear life signs (respiration, circulation, etc.), how do botanists decide when a plant is no longer living? For example, is a freshly picked rose considered dead? (Ben R., Albuquerque, New Mexico)

A: A freshly picked rose is not dead. Plant cell metabolism doesn't stop when someone cuts the rose. If it did, the buds would not open when you place the rose in a vase of water.

[Corel] A cut rose lives on

Even grass chewed and swallowed by a cow is not immediately dead says Alison Kingston-Smith, a microbiologist at IGER (Institute of Grassland and Environmental Research in Aberystwyth, Wales, UK).

It's a tough world inside the first stomach of a cow (the rumen). The temperature is a sweltering 102 degrees Fahrenheit (39 degrees Celsius). No air. Enough stomach acid to drown in. However, plants die slowly. They're programmed to adapt to a changing environment. As the grass struggles in the rumen, it lives long enough to release nutrients for the cow's microbes and to die an orderly death.

When is a plant dead? Before we answer this, let's consider how a cell works. A film-like membrane surrounds each cell. Chemical and electrical gradients exist across the membrane that cause nutrients to pass into the cell and wastes to leave the cell. The two-way traffic is essential for the cell to make energy and therefore survive.

A plant is certainly dead when all of its cells cease producing energy and their cellular membranes are no longer intact.

Is a plant dead if all but 1% of its cells are dead? Probably, says Andrew Groover geneticist from the USDA Forest Service in California. "However, many plant cells are 'totipotent,' meaning a single cell can give rise to a whole new plant."

(Answered Jun. 14, 2002)