General Biology - Roots PDF

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Summary

Biology notes regarding the topic on roots...

Description

characteristics of monocots:

organ of a plant that typically lies below the surface of the soil, can be aerial or aerating, non-leaf, non-nodes bearing parts

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anchorage absorption storage transport vegetative reproduction production of hormones

▹ radicle

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first root that comes from a plant, responsible for the production of primary root cotyledon structure within a seed that contains food for developing embryo, also known as "embryonic leaf" hypocotyl below the cotyledon, gives rise to radicle epicotyl embryonic shoot above the cotyledon primary root root from the main trunk or hypocotyl secondary root roots that arise from the primary root adventitious roots roots that arise from stems, leaves, and other parts of plants

▹ one cotyledon ▹ fibrous root system ▹ scattered vascular bundles (in the stem) ▹ parallel leaf venation ▹ flowers are in multiples of three ▹ monocolpate pollen grains ▹ 22% of angiosperms characteristics of eudicots:

▹ two cotyledons ▹ tap root system ▹ ring-arranged vascular bundles (in the stem) ▹ netlike leaf venation ▹ flowers are in multiples of four or five ▹ tricolpate pollen grains ▹ 75% of angiosperms

▹ the network of all the roots of plants ▹ has two types: — taproot system — fibrous or diffuse system

▹single large root with smaller branch roots ▹ penetrate deeply, well adapted to deep soils where the groundwater is not close to the surface

▹ large numbers of roots nearly equal in size ▹ generally thin, spreading out below the soil surface, no main root ▹best adapted to shallow

▹ found in most eudicot and

soils with light rainfall

gymnosperm plants

▹ found in most monocots and seedless vascular plants

▹ primary growth usually occurs in the entire plant growth in length, produced by apical meristems, involves the production and elongation of roots, stems, and leaves in roots, it produces the epidermis, ground tissues, vascular tissues, and root hairs (which aid absorption by increasing the surface area of epidermal cells)

▹ primary growth usually occurs only in the youngest parts (a.k.a. non-woody)

growth occurs just behind the tip in three zones of cells at successive stages of primary growth, has undefined boundaries thimble-like structure that covers the tip of a root has two types of cells: ▹ inner columella columnarlooking cells ▹ outer, lateral root cap continuously replenished by the root apical meristem functions of the root cap: ▹ protect delicate tissues ▹ secretes a slimy substance to lubricate the soil around the tip of the root ▹ functions in the perception of gravity gravitropism in the root cap amyloplasts in the columella tumble down to the side nearest the source of gravity and the root bends in that direction

▹ includes the root apical meristem and its immediate growth products — the apical meristem is inverted and forms a concave dome located in the center of the root tip in the area protected by the root cap, grows in upward and downward direction ▹ cells divide every 12 to 36 hours toward the dome's edges ▹ produces new root cells, including the root cap

▹ root cells can elongate to more than ten times their original length ▹ where most root lengthening occurs and pushes the tip deeper into the soil

▹ also known as the zone of maturation ▹ where cells complete their differentiation and become distinct cell types ▹ can also develop transport systems, external barriers, and branching root systems...