Featured Research

from universities, journals, and other organizations

Is your leaf left-handed?

Date:
June 23, 2012
Source:
American Society of Plant Biologists
Summary:
The spiral pattern of leaf formation from the point of growth affects the developing leaf's exposure to the plant hormone auxin; This exposure leads to measurable left-right asymmetry in leaf development, in species previously assumed to have symmetric leaves.

Previously overlooked asymmetry has been found in Arabidopsis and tomato leaves.
Credit: Image courtesy of American Society of Plant Biologists

The front of a leaf is different from the back of a leaf and the tip is different from the base. However, a leaf from a tomato or an Arabidopsis plant superficially appears to be bilaterally symmetrical, or the same on the left and right sides. Don't let its appearance fool you; there is an underlying asymmetry between the left and right sides of such leaves -- it just took a while for scientists to discover it. The story begins with the mechanism by which leaves form along a stem. In broad-leafed plants, dicots, leaves form from the meristem, an actively dividing tissue at the top of the plant, so that as you look down the stem, the oldest leaves are at the bottom.

Leaves don't just become arranged by random chance either -- phyllotaxis, the arrangement of leaves or flowers along a stem, affects key plant characteristics, such as how much light can filter through to lower leaves. Leaves can form opposite each other, or in alternation, or in whorls; often leaves form in spirals where the next leaf is offset by roughly 137 degrees, known as the "golden angle," which is related to the Fibonacci sequence.

Recent research has shown that leaf initiation in the meristem is specified by locally high concentrations of the plant hormone auxin. In a study published in The Plant Cell, an international group coordinated by Neelima R. Sinha, Ph.D., of the University of California at Davis, examined how the pattern of auxin concentrations might affect the symmetry of the leaf. She explains, "As leaves are initiated within a spiral context, we might expect that they would be asymmetric and exhibit the same handedness of the spiral, like propeller blades. Yet, superficially many leaves appear symmetrical." To examine whether the spiral pattern of leaves affected symmetry, her team first modeled the anatomy of the forming leaves and the location of the highest concentrations of auxin, finding that the two were not perfectly aligned. Following up, they found that this difference caused asymmetry at both the molecular level, altering gene expression, and the anatomical level, altering leaf shape, in tomato and Arabidopsis thaliana leaves. Indeed, the authors found measurable anatomical differences between the left and right sides of both young and mature leaves, identifying a previously overlooked axis of asymmetry.

Dr. Sinha summarizes: "Our results show that asymmetry is indeed very much present in the leaves around us and that the spiral, within which they are initiated, influences their development from the earliest stages. Quite literally, the handedness of the spiral in plants transmits its asymmetry to leaves. By studying these asymmetries, we can begin to understand the mechanisms by which plants produce such a staggering array of leaf shapes in such regular arrangements."

This work was funded through a National Science Foundation grant (IOS-0820854) andSystemsX.chPlantGrowthRTD.


Story Source:

The above story is based on materials provided by American Society of Plant Biologists. Note: Materials may be edited for content and length.


Journal Reference:

  1. D. H. Chitwood, L. R. Headland, A. Ranjan, C. C. Martinez, S. A. Braybrook, D. P. Koenig, C. Kuhlemeier, R. S. Smith, N. R. Sinha. Leaf Asymmetry as a Developmental Constraint Imposed by Auxin-Dependent Phyllotactic Patterning. The Plant Cell, 2012; DOI: 10.1105/tpc.112.098798

Cite This Page:

American Society of Plant Biologists. "Is your leaf left-handed?." ScienceDaily. ScienceDaily, 23 June 2012. <www.sciencedaily.com/releases/2012/06/120623094318.htm>.
American Society of Plant Biologists. (2012, June 23). Is your leaf left-handed?. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2012/06/120623094318.htm
American Society of Plant Biologists. "Is your leaf left-handed?." ScienceDaily. www.sciencedaily.com/releases/2012/06/120623094318.htm (accessed July 30, 2014).

Share This




More Plants & Animals News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
Raw: Otters Enjoy Water Slides at Japan Zoo

Raw: Otters Enjoy Water Slides at Japan Zoo

AP (July 30, 2014) River otters were hitting the water slides to beat the summer heatwave on Wednesday at Ichikawa City's Zoological and Botanical Garden. (July 30) Video provided by AP
Powered by NewsLook.com
In Virginia, the Rise of a New Space Coast

In Virginia, the Rise of a New Space Coast

AP (July 30, 2014) Every summer, tourists make the pilgrimage to Chincoteague Island, Va. to see wild ponies cross the Assateague Channel. But, it's the rockets sending to supplies to the International Space Station that are making this a year-round destination. (July 30) Video provided by AP
Powered by NewsLook.com
Rodents Rampant in Gardens Around Louvre

Rodents Rampant in Gardens Around Louvre

AP (July 29, 2014) Food scraps and other items left on the grounds by picnickers brings unwelcome visitors to the grounds of the world famous and popular Louvre Museum in Paris. (July 29) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins