Primary plant growth_23.pdf

Cells, Tissues and Organs: Learning objective: Taking a closer look- relationship to plant growth & development • A plant organ is (e.g. leaf, stem, root etc.)_ a combination of different tissue types. Four tissue types in plants . Each tissue_specialised cells Dermal tissue (outer layers) Vascular...

Cells, Tissues and Organs: Learning objective: Taking a closer look- relationship to plant growth & development • A plant organ is (e.g. leaf, stem, root etc.)_ a combination of different tissue types. Four tissue types in plants . Each tissue_specialised cells Dermal tissue (outer layers) Vascular tissue (conducting tissue) Meristematic tissue (sites of cell division) Ground tissue (everything else) Plant anatomy_internal organisation and structure -position of different tissues, -localisation of cells How can this be possible? Meristematic cells Apical meristems (primary meristems_primary plant growth) Lateral meristems (secondary meristems_secondary plant growth) Apical Meristems • Have undifferentiated cells called initials • Responsible for longitudinal development (along the shoot and root axis) of the plant (production of more cells) • Indeterminate growth • Located at the extremities of stems and roots How can a stem grow taller? Apical meristems (primary meristems): Primary plant growth Increase in plant height (grow longitudinally)---Addition of new cells by cell division (increase in cell number), cell expansion (elongation); cell differentiation Maintenance of the axial pattern Throughout plant’s life (indeterminate plant growth) Immature leaves • Shoot tip: Leaf trace: Vascular tissues (stained more intensely -darker) Shoot apical meristem (SAM) And columns of cells at different stages development- cell division, cell expansion & differentiation; More specialised dependent on locations/positions Vascular tissues (vascular bundles) of the shoot or stem Pith Quiz: Is this a Eudicot Shoot apical meristem (SAM): Tunica and Corpus Meristem identity is maintained while new daughter cells are added to increase the length of the shoot axis. New daughter cells: more rounds of cell division; each cell undergoes cell expansion (elongation), increase in cell size (cell volume) & differentiation L.S. L.S. T.S. A B C D T.S. A: epidermis A B C D B: fibre C: phloem D: xylem Developmental relationship between the meristem, dermal tissues, vascular bundles, and ground tissues. All the cells in the shoot axis are derived from the cell division of the shoot apical meristems. During primary plant growth: Meristem identity is maintained while new daughter cells are added to increase the length of the shoot axis. New daughter cells: more rounds of cell division; each cell undergoes cell expansion (elongation), increase in cell size (cell volume) & differentiation into the different types of cells of the epidermis, vascular tissues, and the ground tissues (the cortex , pith etc.) Root apical meristem RAM Further up away from the root tip or root apical meristem: more mature part of the root