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29topic_9a_f07 - Topic 9 Meristems and Primary Plant...

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Unformatted text preview: Topic 9 Meristems and Primary Plant Tissues Primary Plant Tissues Meristematic Tissues Apical Intercalary Simple Primary Tissues Parenchyma Collenchyma Sclerenchyma Complex Primary Tissues Leaf Mesophyll Epidermis Xylem Phloem Meristems Plants differ from animals by having indeterminant growth. Meristems This is because of the presence of meristems where the dividing cells called initials are located. Following cell division, one of the daughter cells remains as an initial and the other is a derivative. Apical Meristem The apical meristem is an area that generates derivatives destined to become the primary meristems. Primary Meristems Primary meristems are areas that generate derivatives which give rise to the tissue areas of the plant body. Primary Meristems These primary meristems are the protoderm, the ground meristem and the procambium that give rise to the epidermis, ground tissue and vascular tissue (stele). Protoderm Epidermis dermal tissue system Ground Meristem Ground Tissues Parenchyma Collenchyma Sclerenchyma Apical Meristem Procambiu m ground tissue system Primary Xylem and Phloem vascular tissue system Dicot Root Tip Dicot Root Tip root hairs Dicot Root Tip emerging roots Dicot Root Tip root cap response to gravity root hairs root apex Root Tip of Corn This is a longitudinal section stained and photographed with a light microscope Root Apical Meristem The root tip actually has two meristematic regions the apical meristem and the root cap. The area circled in yellow is the general vicinity of the apical meristem whose derivatives will become the cells of the three primary meristems The area circled in green is the root cap. Root Apical Meristem The root cap is a special region of disposable cells that protects the root as it pushes through the soil. Three Primary Meristems procambiu m ground meristem protoderm Root Apical Meristem In the root apical meristem itself is a region of few cell divisions called the quiescent region that is probably some sort of control area. The rest of the meristem gives rise to the tissues of the root. The general location of the quiescent region Q uie s c e nt R e g io n o f R o o t Regions of the Root Tip In the root tip there are three areas: the region of cell division, the region of cell elongation and the region of cell maturation. There is also a root hair region Region of Maturation root hair mature xylem epidermis immature xylem endodermis Region of Elongation Region of Cell Division mature phloem immature phloem protoderm procambium ground meristem apical meristem root cap response to gravity root hairs root apex Statoliths Respond to Gravity S T E M T I P Shoot Apical Meristem The shoot apical meristem gives rise to more organs than the root. The shoot apical meristem has two basic regions the tunica, which is peripheral in tunica which the planes of division are perpendicular to the surface, and the corpus which is the rest of the meristem with variable planes of division. There is also a region of central mother cells that is analogous to the root quiescent region that acts as an "organizer region". region" ...
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