To the naked eye, plants may appear passive but they actually engage in long-standing wars to outgrow each other. When a plant succeeded in outgrowing another, it literally "shades" the other plant from much-needed sunlight, which is a key ingredient in its survival.
The plant war doesn't end there. The underdog relies on its built-in internal sensors to escape an impending "shade" created by rival plants. These light sensors can effectively detect dips in blue and red lights, which are the wavelengths absorbed by plants. The light sensors can also distinguish the shade from a rival plant and a passing cloud.
Salk Institute scientists published the amazing discovery in the journal Cell on Dec. 24. The team found that a dip in blue light pushes the plant towards an accelerated growth to beat its rivals.
The findings could be useful in increasing crop productivity. For instance, researchers can come up with ways to optimize growth in fickle plants such as soy and tomato. Gene modification can force these plants to yield greater produce even when grown in shaded and crowded fields.
"With this knowledge and discoveries like it, maybe you could eventually teach a plant to ignore the fact that it's in the shade and put out a lot of biomass anyway," said senior study author and Salk's Plant Molecular and Cellular Biology director Joanne Chory.
New Findings Break Old Notions
The new findings are in direct contrast with old notions in the field, literally. Past studies showed when plants detect a dip in the red light, they activate the growth hormone auxin to outgrow its nearby competitors.
For the first time, the new study found that plants can escape the shade through a different process. The molecular light sensors called cryptochrome reacts to the reduced blue light by triggering the genes responsible for accelerated cell growth.
Cryptochrome is a blue light sensor which is also responsible in telling the plant when to flower. It was first found in plants but later discovered in animals. Cryptochrome is linked to the plant and animal species' circadian rhythm or biological clock.
Cryptochrome's blue light-sensing abilities have long been established but the study is the first time its growth acceleration abilities in shaded environments are discovered.
Plant Versus Plant
For the experiment, the scientists used normal and genetically-modified Arabidopsis (rockcress) plants in a room with limited blue light. In the genetically-modified plants, the cryptochromes or PIF transcription factors are taken out.
PIF is protein type that connects to the DNA so it can control which genes are triggered or switched off. Normally, PIFs binds to phytochromes, which are red light sensors, to switch off growth hormones.
The research team monitored the exchanges made between chromosomes, PIFs and the cryptochromes. The stems' growth rates were also monitored among the two groups of plants.
"We found that cryptochromes contact these transcription factors on DNA, activating genes completely different than what other photoreceptors activate," explained the study's first author Ullas Pedmale, who noted that the phenomenon allows plants to quickly respond to their environment's current light source.
Further research will focus on manipulating the plant's growth response. The study can pave the way for farmers to maximize crop production by studying the mechanism on how plants put out and angle their leaves in relation to neighboring plants.
Photo: Lali Masriera | Flickr
