Health

Warning: Your open-plan office can make you ill

Don't blame other commuters if you catch a cold this winter: blame the people who designed your office. According to a study published in the current issue of Ergonomics, workplace layout has a surprising effect on rates ...

Diseases, Conditions, Syndromes

Research finds few US workers aware of COVID sick leave protections

Even with federal provisions aimed at protecting workers, instances of sick people being unable to take time off tripled during the pandemic and fewer than half of workers were aware that emergency COVID-19 sick leave was ...

Diseases, Conditions, Syndromes

U.S. workers need paid sick leave to stop the spread of coronavirus

The United States Bureau of Labor Statistics reports that almost one-third of Americans do not have access to paid sick leave and 69 percent of part-time workers do not have access. Only the U.S. and Japan do not mandate ...

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Leaf

In 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.

This text uses material from Wikipedia, licensed under CC BY-SA