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never grow woody tissue. They are usually green-stemmed, often short-lived (annuals) and soft. Examples: Herb Robert, stinging nettle, buttercup
do grow woody stems and live for years (they're perennials.) They are relatively low in stature compared to trees, and they lack a central main trunk. A typical shrub will have several stems arising from the ground. Examples: blackberry, Oregon grape, willow
grow woody tissue and can live for centuries. They do have a central trunk. Examples: bigleaf maple, cottonwood, douglas fir
Epidermis (upper and lower)
provides the first layer of protection, protects against water loss, regulates gas exchange, and (especially in roots) absorbs water and mineral nutrients.
special cells allow stomata to close to prevent water loss, or to open to allow air to move in and out.
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