Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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

The role of epidermal cells in determining leaf size and shape

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.

The full article in the link mentioned is available for no charge for 30 days following the date of this summary at After this date, reporters may contact Richard Hund at for a copy of the article.

The Botanical Society of America ( is a non-profit membership society with a mission to promote botany, the field of basic science dealing with the study and inquiry into the form, function, development, diversity, reproduction, evolution, and uses of plants and their interactions within the biosphere. It has published the American Journal of Botany ( for nearly 100 years. In 2009, the Special Libraries Association named the American Journal of Botany one of the Top 10 Most Influential Journals of the Century in the field of Biology and Medicine.

For further information, please contact the AJB staff at

Richard Hund | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Make way for the mini flying machines
21.03.2018 | American Chemical Society

nachricht New 4-D printer could reshape the world we live in
21.03.2018 | American Chemical Society

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

TRAPPIST-1 planets provide clues to the nature of habitable worlds

21.03.2018 | Physics and Astronomy

The search for dark matter widens

21.03.2018 | Materials Sciences

Natural enemies reduce pesticide use

21.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>