+ Identifying Plant Tissues Chapter 4 + Combining Cells to Form Tissues ! Plants grow as cells divide to produce new cells in areas of the plant called meristems. ! After new cells are produced, they specialize for certain functions, enlarging and changing their structure to match their function. ! Cells…..tissues…..tissue systems…..organs + Four Main Types of Tissue Systems ! Meristematic tissue system- contains cells that are actively dividing to produce new plant tissue ! Ground tissue system- contains tissues that make up the bulk of the plant ! Do photosynthesis ! Support ! Store food ! Repair damage + Four Types of Tissue Systems ! Vascular tissue system- conducts water, minerals, and sugars throughout plant ! Dermal tissue system- protect plant and prevents water loss from tissues + Meristematic Tissues ! Meristematic tissues are tissues where cells are actively multiplying to provide new cells for plant growth. ! permanent regions of active cell division ! all purpose cells ! can become any type of plant cell ! small, box-shaped, small vacuoles + Meristematic Tissues ! As the cells enlarge, they begin to differentiate, becoming specialized for a certain function. ! Two plant organ systems- ! Shoot system- above ground, supports leaves, flower, and fruits ! Root system- underground, absorbs water and minerals + Meristematic Tissues ! Four types of meristems ! Apical meristems ! Axillary buds ! Lateral meristems ! Intercalary meristems + Meristematic Tissue - Apical ! Apical Meristems - Found at the tips of roots and shoots. Plants get taller, and roots get longer, from their tips. ! Increase in length as the apical meristems produce new cells (primary growth) ! Divide to produce new cells, which elongate, making roots get longer and shoots get taller. ! Primary Meristems ! Protoderm ! Ground Meristem ! Procambium + Meristematic Tissue – Apical ! Once cells elongate and differentiate into a particular cell type, they usually can’t divide any more due to their rigid cell walls. ! Meristematic cells, however, continue to divide, enabling growth throughout the life of the plant. ! Indeterminate growth- keeps growing throughout life ! Determinate growth- stops growing when reaches maturity + Meristematic Tissues - Lateral !Lateral meristems are thin cylinders of tissue that form in mature regions of shoots and roots of many plants, especially those that produce woody tissue. !They divide to produce secondary growth, growth that increases the diameter [girth] of a shoot [stem or trunk] or root. + Meristematic Tissues - Lateral !Plants have two types of lateral meristems. ! Vascular Cambium – Produces new vascular tissues that function primarily in support and conduction. ! Thin cylindrical cells. ! Cork Cambium - Lies outside vascular cambium just inside the outer bark of woody plants. Meristems and Growth Growth and Meristems + + Meristematic Tissues - Axillary ! Axillary Buds -- produced as stems elongate in the angle between the stem and the petiole of each leaf -- May remain dormant until apical meristem has grown and moved away from the axillary bud. -- When apical meristem is far enough away, the meristems of the axillary bud begins to grow forming a branch. + Meristematic Tissue - Axillary ! Branches can be forced to grow by removing the apical meristem which wakes up the axillary meristem of the main shoot. + Meristematic Tissues ! Grasses and related plants do not have vascular cambium or cork cambium, but do have apical meristems in the vicinity of the nodes. ! Intercalary meristems ! Develop at intervals along stems where they add to stem length- cells get added to the middle to increase length ! This is why you can mow grass and the grass will continue to get longer. + Intercalary Meristem .