Modeling Leaf Mass
April 20, 2017
One science homework assignment that my children had while in elementary school was collecting leaf specimens during the autumn abscission. Our area of Northern New Jersey is heavily forested, so it was easy to find quite a few pristine specimens. The Native Plant Society of New Jersey lists more than a hundred trees and shrubs indigenous to our area.
The most common dicotyledon genera in our area are the Acer (maple), Betula (birch), Fraxinus (ash), Malus (apple), Prunus (plum, cherry), Quercus (oak), Salix (willow), and Ulmus (elm). The front lawn of my house is adorned with two large maple trees. There was another maple on the back lawn, but it was destroyed in a storm of wet snow on October 29, 2011, an event described in this article (Oh No! - October Snow! October 31, 2011).
The difference in the shape of their leaves is one morphological characteristic that defines trees as different species. Elementary school students are shielded from such complications as the species problem, which is the fundamental question of how you define a species. One web site lists 26 ways in which species are defined. Modern technology has either helped, or complicated, species identification by DNA barcoding, which uses genetic markers to identify species. This method, however, is of no help in the identification of fossil species.
The vast diversity of leaf shapes and sizes is an indicator of the diversity of cells and tissues from which they are composed. The leaf dry mass per unit leaf area (LMA) is an easily measured quantity obtained by weighing a dried leaf and dividing this weight by the original fresh area.[3-4] LMA is used extensively in plant biology to predict such things as the rate of photosynthesis, nitrogen content and the suitability of a plant for a particular environment. However, the relationship of LMA to the types of cells and tissues of a leaf, their numbers and sizes has not been studied.
Biologists from the University of California (Los Angeles, California), the University of Sydney (Narrabri NSW Australia), the Universidad de Córdoba Edificio Celestino Mutis (Córdoba, Spain), and Forschungszentrum Jülich GmbH (Jülich, Germany), have developed a mathematical model of leaf mass area that produced an equation for leaf mass area based on the dimensions and numbers of cells of each type in the leaf. This is the first time that the diversity of cells and tissues that comprise a leaf have been related to the overall leaf morphology.
As global warming proceeds, LMA can be a useful indicator of how plants adapt to the warming environment. Says Grace P. John, the lead author of the paper describing this research in the UCLA Department of Ecology and Evolutionary Biology,
"It is hard to exaggerate the importance of LMA in plant biology — it’s like body size in animal ecology, facial symmetry for the psychology of attraction, and sprint speed for NFL wide receivers... LMA has really been the 'uber' variable for understanding plant economics, productivity and function."
John, a Ph.D. candidate in ecology and evolutionary biology at UCLA, studied the anatomy of eleven species growing on the grounds of UCLA. She cross-sectioned the leaves to catalogue the sizes and numbers of cells, and she stained whole leaves to measure the vein tissues. The team then developed a model and an equation that predicts the leaf mass area from just the leaf structures.
As shown in the figure below, the leaf structures are the upper cuticle (UC), lower cuticle (LC), upper and lower epidermis (UE and LE), the central spongy and palisade mesophyll cells (SP and PA) where photosynthesis occurs, veins (V), that are wrapped in a ring of cells known as the bundle sheath (BS), and the bundle sheath extensions (BSE). The cells were modelled as cylinders, capsules, and spheres, depending on their principal shape.
The equation is able to predict LMA for the analyzed species in the range of 33-262 g/m2 with a high accuracy (R2 = 0.94, see figure). High LMA results principally from larger cell sizes, higher cell mass densities, a greater numbers of mesophyll cell layers, and a greater major vein allocation. Says John, "With our approach, we show that evergreen leaves tend to be tougher and live longer because they have larger and denser cells."
Lower leaf mass area is generally indicative of greater plant growth and productivity, while higher leaf mass area makes a plant less stress tolerant, so this research can aid in an understanding of how differences at the cellular level affect the productivity and tolerance to environmental stress of species. It might also assist in the development of designer crops for particular applications. This research was funded by the National Science Foundation.
- Plants by New Jersey County, Native Plant Society of New Jersey Web Site.
- John S. Wilkins, "A list of 26 Species Concepts," Science Blogs, October 1, 2006.
- Grace P. John, Christine Scoffoni, Thomas N. Buckley, Rafael Villar, Hendrik Poorter, and Lawren Sack, "The anatomical and compositional basis of leaf mass per area," Ecology Letters, February 14, 2017, http://dx.doi.org/10.1111/ele.12739.
- Researchers develop equation that helps to explain plant growth, UCLA Press Release, March 7, 2017.
Permanent Link to this article
Linked Keywords: Science; homework assignment; child; children; elementary school; leaf; sample; specimen; autumn; abscission; Northern New Jersey; forest; forested; Native Plant Society of New Jersey; tree; shrub; indigenous; dicotyledon; genus; genera; Acer (maple); Betula (birch); Fraxinus (ash); Malus (apple); Prunus (plum, cherry); Quercus (oak); Salix (willow); Ulmus (elm); lawn; house; winter storm; New Jersey; Habitat Restoration; U.S. Fish and Wildlife Service; morphology (biology); morphological; species; species problem; technology; DNA barcoding; gene; genetic; fossil; cell; tissue; dry matter; dry mass; area; analytical balance; weighing; botany; plant biology; reaction rate constant; rate; photosynthesis; nitrogen; environment; biologist; University of California (Los Angeles, California); University of Sydney (Narrabri NSW Australia); Universidad de Córdoba Edificio Celestino Mutis (Córdoba, Spain); Forschungszentrum Jülich GmbH (Jülich, Germany); mathematical model; equation; global warming; Grace P. John; author; scientific literature; paper; research; UCLA Department of Ecology and Evolutionary Biology; allometry; body size; animal; ecology; facial symmetry; psychology; physical attractiveness; sprint speed; National Football League; NFL; wide receiver; variable; economics; Doctor of Philosophy; Ph.D. candidate; graduate school; plant anatomy; cross-section; staining; stain; vein; plant cuticle; epidermis; palisade cell; mesophyll; vascular bundle; bundle sheath; cylinder; capsule; sphere; Leaf; California live oak (Quercus agrifolia); prediction; accuracy; correlation coefficient; density; evergreen; life expectancy; regression validation; Cartesian coordinate system; graph; Gnumeric; stress; genetically modified crop; designer crop; National Science Foundation.
Latest Books by Dev Gualtieri
Thanks to Cory Doctorow of BoingBoing for his favorable review of Secret Codes!
Blog Article Directory on a Single Page
- J. Robert Oppenheimer and Black Holes - April 24, 2017
- Modeling Leaf Mass - April 20, 2017
- Easter, Chicks and Eggs - April 13, 2017
- You, Robot - April 10, 2017
- Collisions - April 6, 2017
- Eugene Garfield (1925-2017) - April 3, 2017
- Old Fossils - March 30, 2017
- Levitation - March 27, 2017
- Soybean Graphene - March 23, 2017
- Income Inequality and Geometrical Frustration - March 20, 2017
- Wireless Power - March 16, 2017
- Trilobite Sex - March 13, 2017
- Freezing, Outside-In - March 9, 2017
- Ammonia Synthesis - March 6, 2017
- High Altitude Radiation - March 2, 2017
- C.N. Yang - February 27, 2017
- VOC Detection with Nanocrystals - February 23, 2017
- Molecular Fountains - February 20, 2017
- Jet Lag - February 16, 2017
- Highly Flexible Conductors - February 13, 2017
- Graphene Friction - February 9, 2017
- Dynamic Range - February 6, 2017
- Robert Boyle's To-Do List for Science - February 2, 2017
- Nanowire Ink - January 30, 2017
- Random Triangles - January 26, 2017
- Torricelli's law - January 23, 2017
- Magnetic Memory - January 19, 2017
- Graphene Putty - January 16, 2017
- Seahorse Genome - January 12, 2017
- Infinite c - January 9, 2017
- 150 Years of Transatlantic Telegraphy - January 5, 2017
- Cold Work on the Nanoscale - January 2, 2017
- Holidays 2016 - December 22, 2016
- Ballistics - December 19, 2016
- Salted Frogs - December 15, 2016
- Negative Thermal Expansion - December 12, 2016
- Verbal Cues and Stereotypes - December 8, 2016
- Capacitance Sensing - December 5, 2016
- Gallium Nitride Tribology - December 1, 2016
- Lunar Origin - November 27, 2016
- Pumpkin Propagation - November 24, 2016
- Math Anxiety - November 21, 2016
- Borophene - November 17, 2016
- Forced Innovation - November 14, 2016
- Combating Glare - November 10, 2016
- Solar Tilt and Planet Nine - November 7, 2016
- The Proton Size Problem - November 3, 2016
- Coffee Acoustics and Espresso Foam - October 31, 2016
- SnIP - An Inorganic Double Helix - October 27, 2016
- Seymour Papert (1928-2016) - October 24, 2016
- Mapping the Milky Way - October 20, 2016
- Electromagnetic Shielding - October 17, 2016
- The Lunacy of the Cows - October 13, 2016
- Random Coprimes and Pi - October 10, 2016
- James Cronin (1931-2016) - October 6, 2016
- The Ubiquitous Helix - October 3, 2016
- The Five-Second Rule - September 29, 2016
- Resistor Networks - September 26, 2016
- Brown Dwarfs - September 22, 2016
- Intrusion Rheology - September 19, 2016
- Falsifiability - September 15, 2016
- Fifth Force - September 12, 2016
- Renal Crystal Growth - September 8, 2016
- The Normality of Pi - September 5, 2016
- Metering Electrical Power - September 1, 2016
Deep Archive 2006-2008