Imagine a world where farmers could avoid crop-killing droughts or frost and where florists could grow an
abundance of flowers all year long.
Scientists are within reach of this possibility because of genetic plant studies conducted by a UNT researcher and his colleague. Brian Ayre, UNT professor of biology, and Robert Turgeon, Cornell University professor of biology, have demonstrated that introducing a specific gene (out of the 25,000 or so genes in a plant) to a leaf can cause a plant to flower.
Scientists have been working to understand the chemical nature of the flowering process for more than 75 years, and now Ayre and Turgeon are one step closer to finding the answer. Their discovery could make it possible for farmers to get a yield from several planting cycles, increasing food production. The outcome of their research could also help florists save money normally spent to force plants to bloom out
"Understanding what stimulant causes a plant to flower could be the key to increasing crop and flower production," Ayre says. "Plants that typically only bud in the summer could also bud in the spring. Crops could be stimulated to have a double harvest."
‘The Holy Grail'
Ayre and Turgeon conducted research for two years to learn more about what causes plants to flower. They started with a blueprint based on what scientists already know about plants.
"Plants can tell the season and the length of day," Turgeon says. "And what was found a long time ago is that this perception takes place in a plant's leaves, but it's not the leaves that flower."
Research shows that the transition to reproductive growth occurs far from the leaves, at the tip of the plant known as the meristem.
"A signal must be transmitted from the leaves to the meristem," Ayre says. "This signal has a name, florigen, but the problem in identifying it has been so perplexing that scientists refer to it as the Holy Grail of plant biology."
Understanding that the perception of light in one part of
a plant causes a response in another part, Ayre and Turgeon studied which signals were transported through the veins of a plant, causing it to flower.
"We manipulated the phloem — the plumbing system of the plant — at a molecular level," Turgeon says.
A stimulating gene
Their research focused on a single gene called CONSTANS (CO). Scientists knew that CO played a role in the flowering process, but what role was unclear — it was thought to be a product of florigen, functioning at the plant's tip.
To discover more about how the gene works, Ayre and Turgeon increased the amount of CO in a plant called Arabidopsis, which is similar to a mustard plant.
Flowering was accelerated under day-length conditions that normally delay the plant's flowering. The researchers then grafted portions of the Arabidopsis plant to vegetative tips from plants that had no CO. As a result, the plants that had been grafted began to flower immediately after the graft junctions healed.
"With this experiment, we demonstrated that a CO-derived signal in a leaf is transported to the plant's tip," Ayre says. "Our work suggests that CO is a precursor to florigen, rather than a product of it."
Ayre says that at the molecular level, the CO gene can switch the florigen signal on or off, depending on day length.
"The discovery of the role of CO in the florigen process could mean that certain plants will not be dependent upon the prevailing environmental conditions in order to reproduce," Ayre says.
Typically, short-day plants such as strawberry, rice, soybean, sorghum and cotton flower in late fall, winter or early spring. Long-day plants such as oats, peas and canola flower in late spring and summer. Ayre says introducing CO into short-day plants as well as long-day plants could increase production.
In addition, flower producers may no longer have to mask their green houses to force short-day plants like zinnia, dahlia and African marigolds to bloom in the summer, or depend on expensive lighting systems to artificially extend winter days for plants like fuschia and begonia.
"The role of CO in generating flowering brings us closer to having an abundance of affordable vegetables and flowers year round," Ayre says.