Featured Research

from universities, journals, and other organizations

Can a single layer of cells control a leaf's size?

Date:
March 15, 2010
Source:
American Journal of Botany
Summary:
Little is known about the developmental control of leaf size and shape, and understanding the mechanisms behind this is a major issue in plant biology. New research concludes that communication between adjacent cell layers plays an important role in determining leaf size. Cells in one tissue layer can control the rate of division of cells in another tissue layer, which in turn influences overall leaf size.

The extent of cell division in the leaf epidermis alters the extent of cell division in the mesophyll and is a factor regulating blade expansion and ultimate leaf size.
Credit: Courtesy of Michael Marcotrigiano, Smith College, Northampton, MA.

Ever looked carefully at the leaves on a plant and noticed their various sizes and shapes? Why are they different? What controls the size and shape of each individual leaf? Very little is known about the developmental control of leaf size and shape, and understanding the mechanisms behind this is a major issue in plant biology.

A leaf's size is determined by a combination of cell number, cell size, and intercellular space. Michael Marcotrigiano from Smith College, Massachusetts, wanted to find out what role cell layers played in regulating leaf size and shape. He utilized a powerful tool -- the synthesis of graft chimeras -- that has allowed him to carefully analyze the developmental regulation of leaf size and shape in Nicotiana and has published his findings in the February issue of the American Journal of Botany.

By grafting plants of different Nicotiana genotypes Marcotrigiano was able to recover shoots from the graft union that were chimeras. These shoots were composed of both genotypes. Eventually he recovered leaves with two genetically distinct cell layers. He grafted N. tabacum, a large-leaf genotype, and N. glaucum, a small-leaf genotype, to produce leaves where the resulting epidermal cell layer was a different genotype than the mesophyll cell layer -- but on only one side of the leaf, allowing for direct comparison of the growth of the leaf from one side to the other. Thus, one side of the leaf could act as a "control" for the other side of the leaf. This enabled him to set up some nicely designed comparisons where on one side of the leaf the outer cell layer (the epidermis) differed in genotype from the rest of the leaf.

"Since leaves generally vary in size along the length of the stem and leaf size is strongly influenced by environmental factors, my method allowed me to compare one side of a leaf to the other, negating the complications that arise when comparing different leaves on a single plant or leaves on different plants," Marcotrigiano said.

Creating these graft chimeras was time-consuming and involved an element of chance; often the growing tip of the chimeral shoots reverted back to a non-chimeral shoot rendering the leaves generated from that point on useless for analysis. However, over the past decade enough leaves were recovered that were perfectly bisected, homogeneous on one side of the midvein and with a unique epidermis on the other. This allowed Marcotrigiano to use them to examine how leaf cell layer affects leaf size and shape.

Marcotrigiano's most striking finding was the important role that the epidermal cells played in determining leaf size. He found that leaves grew asymmetrically when one side of the midvein contained identical cell layer arrangements and the other side contained epidermal cells that differed genetically from the mesophyll cells. When big-leaf epidermal cells surrounded small-leaf mesophyll cells in an otherwise all small-genotype leaf, the big-leaf epidermal cells caused that side of the leaf to be bigger than the other side. In contrast, when small-leaf epidermal cells surrounded big-leaf mesophyll cells in an otherwise all big-genotype leaf, the small-leaf epidermal cells caused that side to be smaller than the other side.

Epidermal cells not only controlled overall leaf size, but also influenced the number of cells produced in the mesophyll layer. For example, small-leaf epidermal cells surrounding big-leaf mesophyll cells caused the mesophyll cells to have many fewer cell divisions than when they were surrounded by big-leaf epidermal cells. Interestingly, the epidermal cells did not influence, or change, the size of the mesophyll cells.

Marcotrigiano concludes that while regulation of leaf size is complex and influenced by many factors and many genes, his findings show that communication between adjacent cell layers plays an important role in determining leaf size. Cells in one tissue layer can control the rate of division of cells in another tissue layer, which in turn influences overall leaf size.


Story Source:

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


Journal Reference:

  1. Marcotrigiano et al. A role for leaf epidermis in the control of leaf size and the rate and extent of mesophyll cell division. American Journal of Botany, 2010; 97 (2): 224 DOI: 10.3732/ajb.0900102

Cite This Page:

American Journal of Botany. "Can a single layer of cells control a leaf's size?." ScienceDaily. ScienceDaily, 15 March 2010. <www.sciencedaily.com/releases/2010/02/100225140902.htm>.
American Journal of Botany. (2010, March 15). Can a single layer of cells control a leaf's size?. ScienceDaily. Retrieved September 17, 2014 from www.sciencedaily.com/releases/2010/02/100225140902.htm
American Journal of Botany. "Can a single layer of cells control a leaf's size?." ScienceDaily. www.sciencedaily.com/releases/2010/02/100225140902.htm (accessed September 17, 2014).

Share This



More Plants & Animals News

Wednesday, September 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Ivorians Abandon Monkey Pets in Fear Over Ebola Virus

Ivorians Abandon Monkey Pets in Fear Over Ebola Virus

AFP (Sep. 16, 2014) Since the arrival of Ebola in Ivory Coast, Ivorians have been abandoning their pets, particularly monkeys, in the fear that they may transmit the virus. Duration: 00:47 Video provided by AFP
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