Gene spurt for grazed plants described in articles in University of Illinois News 1 August 2011 and ScienceDaily 3 August 2011. It has long been observed that some plants can not only re-grow after being partially eaten by grazing animals, but actually experience a growth spurt, with an increase in overall size and reproductive fitness, i.e. more flowers and fruit, beyond what they had before. A group of scientists have found one of the ways this happens by studying two different cultivars of Arabidopsis thaliana (mustard cress) that differ in how well they re-grow after grazing. The researchers simulated the effects of grazing by clipping the plants’ central stems and then observed the re-growth of stems and leaves and level of seed production, then compared these to unclipped plants of the same cultivar. One cultivar, named Columbia, responded with a large increase in overall growth as well as producing more seeds than unclipped plants. The other, named Landsberg erecta, continued to grow steadily but did not boost its growth or fruitfulness after clipping.
The researchers then studied the cells and chromosomes of the two cultivars before and after clipping and found the Columbia had duplicated its chromosomes many times over, but the Landsberg erecta had not. Ken Paige of the University of Illinois, who led the study, explained: “The overall DNA content goes up in one of the cultivars after clipping, but it doesn’t change in the other. And we think it’s that added boost that increases its reproductive success”. The researchers suggest the extra DNA in the cells enables the plants to increase the production of proteins needed for re-growth and flower and seed production. The cells with extra chromosomes are also larger, so the overall size of the plant is larger. The increase in chromosome number is called endoreduplication, and involves duplicating the plant’s entire set of chromosomes. The increase can be quite dramatic. Arabidopsis plants all start life with 10 chromosomes, but after being grazed on, the cells in regrowth areas have been found to develop repeated chromosome duplications with some plant cells ending up with 320. Daniel Scholes, who was also involved in the study, commented: “We tend to think that what you inherit is what you’re stuck with. But we’re finding that plants are increasing what they have, and for the first time we’re beginning to understand how they do that, and why”. Ken Paige went on to say: “We’ve tracked the plants through generations, so we know that the ones that get eaten actually have up to a three-fold reproductive advantage over the ones that are never eaten. Now we are beginning to understand the molecular mechanisms that make this possible”
Editorial Comment: By duplicating its original chromosomes at the nibbled ends, the plant is not gaining any new genetic information. The plant is duplicating the DNA information it already has and as a result it can make more use of the DNA information which is hugely beneficial to the plant, and at the same time results in a guaranteed food supply for any creatures that eat them. The process described above is only one of a number of mechanisms built into plants that maintain them as a perpetual food supply for animals.
Genesis tells us God made the green plants as food for both animals and man in a fully vegetarian and sustainable world. Plants were a designed part of a planned ecosystem which meant there was no evolutionary struggle between plants and herbivores – they were made for each other and made to survive and the evidence above is fully supportive of this.
After the Fall of Man, God cursed the ground, and both plants and animals and man have degenerated in many ways. The cultivars in the study described above that do not respond to grazing with a growth spurt seem to have lost this ability, and as a result they now have a more fragile existence since they can be eliminated much more easily by grazing. Natural selection can only act against them. Change yes; Evolution no. (Ref. botany, vegetation, polyploidy)
Evidence News 23 May 2012