In a striking revelation, scientists have discovered that all plants live and die by a precise and simple rule. Scientists have found for the first time that plants can self-regulate their populations to maintain stability and optimize their lives, and that the lengths of their lives are precisely related to their mass. Even more incredible, a single scaling power for lifespan holds true across the entire spectrum of plants, from minute single-celled phototrophs to the massively majestic redwoods.
Scientists previously understood that animals’ lifespans are somewhat scaled to the species’ body size, with elephants living much longer than mice. Plant biologists have predicted a similar connection in plants, but a full study had never been conducted until recently.
Researchers Núria Marbà, Carlos Duarte and Susana Agustí at the Mediterranan Institute for Advanced Studies—a joint institute between the CSIC (Spanish Council for Scientific Research) and the University of the Balearic Islands in Esporles, Spain examined more than 1,000 reports of plant birth and mortality rates across a wide spectrum of species, discovering that the connection holds with extreme precision.
The researchers found that both population mortality rates and population birth rates of all plant species scale as the –1/4 power of plant mass. In other words, the smaller a plant, the higher its mortality and birth rates, meaning the shorter its lifespan. Hence, plant lifespan scales as almost exactly the 1/4 power of plant mass.
“The functioning of biological systems depends to a large extent on their metabolism, i.e., on how they process energy and materials, such as light, water, and nutrients,” Marbà explained to PhysOrg.com. “Small plants require fewer resources per unit of time than large ones, and, therefore, they are able to turn over the individuals of their populations faster than large plants. As plant size increases, more resources and time are needed to produce a fully grown individual, and thus their lifespan increases, resulting in small plants having shorter life spans than larger ones.”
One very interesting aspect of these relationships is that mortality and birth rates is nearly identical within a species, keeping the population stable. Nature has clever reasons for this perfect cycle, which include stabilizing carbon cycling, optimizing plant life histories, and stabilizing the ecosystems the plants inhabit. The scientists suggest that, to achieve this balance, plant mortality rates have evolved to match the birth rates.
Although they have found the delicate balance between mortality and birth rates, the actual mechanisms governing plant life and death are still unknown. Controls probably include an assortment of metabolic processes interacting at all levels, from molecular on up, which would include respiration, reproduction, cellular damage, and structural imbalances. Plants retain their reproductive capacity throughout their lives, unlike animals. Therefore, evolution might put greater selective pressure on plants’ lifespans. Similar studies are bring planned to continue the effort to unlock the many mysteries of the green kingdom.
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