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.
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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 ...
Experts: Flu victims should miss work despite lean staffs, lost pay
Sep 23, 2009 |
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It's common sense: Stay home from work if you have the H1N1 flu virus. But the reality of making that happen is daunting for already-lean businesses in Minnesota as they grapple with just how flexible they can be with sick ...
Why are autumn leaves red in America and yellow in Europe?
Aug 13, 2009 |
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Walking outdoors in the fall, the splendidly colorful leaves adorning the trees are a delight to the eye. In Europe these autumn leaves are mostly yellow, while the United States and East Asia boast lustrous ...
High construction cost for cycads
Jul 23, 2009 |
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Self-sustaining organisms like plants possess the ability to synthesize their own food using inorganic materials. Plants use water and carbon dioxide to begin this process in their green tissues. The leaf ...
Trees evolved camouflage defense against long extinct predator: First evidence of camouflage defense in plants
Jul 22, 2009 |
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(PhysOrg.com) -- Many animal species such as snakes, insects and fish have evolved camouflage defences to deter attack from their predators. However research published in New Phytologist has discovered that t ...
Desert rhubarb -- a self-irrigating plant
Jul 01, 2009 |
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Researchers from the Department of Science Education-Biology at the University of Haifa-Oranim have managed to make out the "self-irrigating" mechanism of the desert rhubarb, which enables it to harvest 16 ...
Jobs appears closer to returning to work at Apple
Jun 24, 2009 |
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(AP) -- Apple co-founder and CEO Steve Jobs appears to be a step closer to returning to work, as a doctor gave him an "excellent prognosis" after receiving a liver transplant at a Tennessee hospital.
Jobs sounds 'healthy, energetic': Apple co-founder
May 27, 2009 |
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Apple chief executive Steve Jobs sounds healthy, a month before his scheduled return from a medical leave of absence, Apple co-founder Steve Wozniak was quoted as saying on Wednesday.
Repeatedly working when ill boosts risk of long term sick leave
Apr 30, 2009 |
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Repeatedly going to work when ill significantly boosts the chances of having to take long term sick leave later on, reveals research published ahead of print in the Journal of Epidemiology and Community Health.
Weak social ties at workplace increase risk of burn-out
Apr 09, 2009 |
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Long-term leaves of absence tied to stress-related diagnoses are often preceded by a long period without any secure and comforting social relations. This is shown in a recently published study in public health science at ...
Studies link maternity leave with fewer C-sections and increased breastfeeding
Jan 05, 2009 |
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Two new studies led by researchers at the University of California, Berkeley, suggest that taking maternity leave before and after the birth of a baby is a good investment in terms of health benefits for both mothers and ...
