1 Beneath the palisade layer is the spongy layer. 2  The cells of the spongy layer are more branched and not so tightly packed, so that there are large intercellular air spaces between them for oxygen and carbon dioxide to diffuse in and out of during respiration and photosynthesis. leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Foliage is a mass noun that refers to leaves collectively. Typically a leaf is a thin, dorsiventrally flattened organ, borne above ground and specialized for photosynthesis.
A rift valley is a lowland region formed by the interaction of Earth's tectonic plates. This small rift valley has a typical formationâlong, narrow, and deep. It was formed by the Thingvellir rift, where the North American and Eurasian tectonic plates are tearing, or rifting, apart over a hotspot on the island of Iceland.
Adventure holidays in Africa's Great Rift Valley From the Middle East to east Africa and through bottomless lakes to soaring volcanoes, we select 10 ways to experience the stunning 3,700-mile fault line that is the Great Rift Valley Gallery: Africa's Rift Valley from above