Leaf
hideIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat (laminar) and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In either case, the adaption was made at the expense of water loss. In the Devonian period, when carbon dioxide concentration was at several times its present value, plants did not have leaves or flat stems. Many bryophytes have flat, photosynthetic organs, but these are not true leaves. Neither are the microphylls of lycophytes. The leaves of ferns, gymnosperms, and angiosperms are variously referred to as macrophyll, megaphylls, or euphylls.
Leaves are also the sites in most plants where transpiration and guttation take place. Leaves can store food and water, and are modified in some plants for other purposes. The comparable structures of ferns are correctly referred to as fronds. Furthermore, leaves are prominent in the human diet as leaf vegetables.
For more information about Leaf, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with leave
Poor leadership poses a health risk at work
Nov 02, 2009 |
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Perceived poor managerial leadership increases not only the amount of sick leave taken at a workplace, but also the risk of sickness amongst employees later on in life. The longer a person has had a "poorer" manager, the ...
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Canadian woman loses benefits over Facebook photo
Nov 22, 2009 |
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(AP) -- A Canadian woman on long-term sick leave for depression says she lost her benefits because her insurance agent found photos of her on Facebook in which she appeared to be having fun.
UWM study explores why women leave engineering careers
Other Sciences / Social Sciences
Nov 06, 2009 |
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While only one in 10 male engineers leave their field by the time they reach their 30s, about one in four women are not working in engineering despite having completed the necessary education.
Astronauts get extra moving time at space station
Space & Earth / Space Exploration
Nov 20, 2009 |
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(AP) -- The astronauts aboard the shuttle-station complex are getting some extra moving time.
Men leave: Separation and divorce far more common when the wife is the patient
Nov 10, 2009 |
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A woman is six times more likely to be separated or divorced soon after a diagnosis of cancer or multiple sclerosis than if a man in the relationship is the patient, according to a study that examined the role gender played ...
Poor countries see troubling rise in breast cancer
Nov 02, 2009 |
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(AP) -- Nurses were training women in rural Mexico to examine their breasts for cancer when one raised her hand to object. If she lost her breast, Harvard public health specialist Felicia Knaul recalls the woman saying, ...
1 conjoined twin talking after separation surgery
Nov 19, 2009 |
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(AP) -- A Bangladeshi toddler separated this week from her conjoined twin sister was talking and behaving normally Thursday after waking from a medically induced coma, the head of the surgery team said.
Involving family in medical rounds benefits both family and medical team
Nov 24, 2009 |
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Involving family members of pediatric cancer and hematology patients in medical rounds benefits both the family and the medical team, according to a new Indiana University School of Medicine study.
Extinct goat was cold-blooded
Nov 18, 2009 |
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(PhysOrg.com) -- An extinct goat that lived on a barren Mediterranean island survived for millions of years by reducing in size and by becoming cold-blooded, which has never before been discovered in mammals.
Variable Temperatures Leave Insects wtih a Frosty Reception
Nov 25, 2009 |
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(PhysOrg.com) -- For the first time, scientists at The University of Western Ontario have shown that insects exposed to repeated periods of cold will trade reproduction for immediate survival.
Nokia N900 now available in US
Electronics / Consumer & Gadgets
Nov 18, 2009 |
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Nokia today announced that the highly anticipated Nokia N900 is now on sale in the United States and shipping to consumers who jumped on the opportunity to be among the first to pre-order the Maemo-powered ...
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