Presentation on theme: "1 Review What are three important functions of stems Explain How does the arrangement of vascular bundles in monocot stems differ from dicot stems Apply."— Presentation transcript:
1 1 Review What are three important functions of stems Explain How does the arrangement of vascular bundles in monocot stems differ from dicot stems Apply Concepts How do the functions of a stem relate to the functions of the roots and leaves of a plant 2 Review Define primary and secondary growth Predict Describe what would happen over time to a tree sapling that could grow only taller, not wider
3 Stem Functions Stems produce leaves, branches, and flowers Stems hold leaves up to the sunStems transport substances throughout the plant.
4 Anatomy of a StemEpidermal cells have thick cell walls and a waxy protective coating.
5 Anatomy of a Stem Nodes Buds Where leaves are attachedBudsContain apical meristems that can produce new stems and leavesStems produce woody tissue in larger plants.
6 Monocot StemsClusters of xylem and phloem tissue are scattered throughout the stemGround tissue is fairly uniform consisting mainly of parenchyma cells.
7 Dicot Stems Vascular bundles are arranged in a cylinder, or ring Pith Parenchyma cells inside the ring of vascular tissueCortexParenchyma cells outside the ring of vascular tissue.
8 Primary GrowthGrowth that occurs at the apical meristems.
9 Secondary GrowthStems increase in thickness to support larger plant.
10 Secondary GrowthVery common among dicots and non-flowering seed plants such as pinesRare in monocotsDicots have meristems within stems and roots that produce true secondary growthDicots can grow much larger.
11 Conifers and Dicots Secondary growth takes place in meristems called: Vascular cambiumProduces vascular tissues and increases the thickness of stems over timeCork cambiumProduces the outer covering of stems.
12 Vascular cambium appears as a thin, cylindrical layer of cells between the xylem and phloem of each vascular bundle.
13 Divisions in the vascular cambium give rise to new layers of xylem and phloem Cambium continues to produce new layers of vascular tissue each year, causing the stem to become thicker.
14 Formation of Wood Most of “wood” is actually layers of secondary xylem HeartwoodOlder xylem near the center of the stem no longer conducts water.
15 SapwoodActive in fluid transport and is usually lighter in color.
16 Tree Rings Spring growth As growing season continues Vascular cambium begins to grow rapidly, producing large, light-colored xylem cells, resulting in a light- colored layer of early woodAs growing season continuesCells grow less and have thicker cell walls, resulting in a layer of darker woodThick rings good growing conditions and thing rings poor growing conditions.
17 Formation of Bark Bark All tissues found outside the vascular cambium Tissues include phloem, the cork cambium, and cork.
18 Cork cambium produces a thick, protective layer of waterproof cork that prevents water loss.