How plants assure species survival independently of life span demystified

Botanists have for the first time formulated a universal rule that could help explain the equilibrium of plant species - how plants assure the survival of their species whether their lives last a day or are prolonged over centuries.

Washington, Sept 19 : Botanists have for the first time formulated a universal rule that could help explain the equilibrium of plant species - how plants assure the survival of their species whether their lives last a day or are prolonged over centuries.

The study, scheduled for publication in the forthcoming issue of the journal Proceedings of the National Academy of Science, also concludes that the life span of these organisms might be sensitive to rises in temperature.

According to the authors, the mortality of plants could increase by 40 percent if land temperatures rise by up to 4�C (the rate of increase projected for the 21st century by climate change prediction models).

As part of their study, the scientists examined the mortality and population growth rates of 700 phototrophs, ranging from the very smallest - the cells of the marine photosynthetic cyanobacteria Prochloroccocus up to the largest species of trees.

The researchers searched for general rules conducive to an improved understanding of plant life span regulation.

The authors found that the phytoplankton was the shortest living beings, with a span of around one day, while some trees reached ages of a thousand years.

The researchers said the same basic rules governed the longevity and birth rates of plants, such that the brief life span of the microscopic phytoplankton cells was offset by the vertiginous birth rates of populations, while centennial tree populations registered no more than sporadic births.

They said their findings had provided the key to a universal regulation of the life span of photosynthetic organisms with reference to plant size and the temperatures they grew at. The study also suggested that the mortality rates of phototrophs evolved to match population growth rates, they said.

"A further conclusion is that plant mortality is of necessity highly temperature-sensitive, such that climate change will tend to accelerate the phototroph death rates which are an essential part of the food chain," the authors wrote in their study.

The scientists said the balance between longevity and birth rates in photosynthetic organisms was what kept their populations stable.

"In the event of a serious mismatch between plant mortality and birth rates, these populations would either be driven to extinction (if death rates far exceeded births) or would outgrow available resources of light, water and food with the same inevitable result (in the case of births far exceeding deaths)," the study added.

ANI