Transcript 22.1 Plants
Introduction to Plants Chapter 22.1 Basic Plant Structure Plants Are… 1) 2) 3) 4) Multicellular Eukaryotic Autotrophic Use Chlorophyll a or b How Did Plants Originate? First land plants appeared 500 mya Resembled present day mosses Released nitric acids on rock surfaces which created soil Likely colonies of protists adapted to dry environment…but how? Links Between Algae and Plants Both have protective cell walls Both contain chlorophyll used in photosynthesis Both store food in the form of starches Plants Must Adapt To Live On Land 1. 2. 3. Absorb nutrients from surroundings Prevent desiccation Reproduce without the aid of water If plants adapt to these strategies, they can evolve on land Why would a plant “want” to move onto the land? A. Preventing Water Loss Cuticle: waxy coating that prevents tissues from drying out Stomata-openings in the cuticle that allow gas exchange to take place and also regulate water loss Prevent Desiccation? Desiccation= Drying Out As plants evolved further away from water, they needed to evolve a waterproof structure/coating (cuticle) But, this structure needs pores (stomata) WHY? Think about what the plant needs for photosynthesis… CARBON DIOXIDE! Stomata B. Autotrophic Leaf-organ that enables the plant to trap and absorb light energy Leaf Layers via microscope C. Stabilization and Nutrient Absorption (Accomplished with roots and mycorrihizea) Roots-organ that is used to reach and transport water and minerals, anchor plants and store food Earliest roots are rhizoids Fossils show fungi “helped” plants before roots evolved The Root Main function = absorb water Functional Part = root hair Structure from outside in: – Epidermis with root hair= protection – Cortex=support/storage – Vascular Bundle: Phloem, Vascular Cambium*, Xylem *Vascular Cam: growth of new vascular tissue Root Structure D. Transportation System Stem- Transport of water, food, and minerals Support of plant Storage of materials Structures of the Stem Epidermis (bark or green)=protection Cork cambium =new growth of bark/ epidermis Cortex = thick layer, sometimes contains chloroplasts, mostly for support Vascular Bundle = contain transport tissues towards the middle of the stem Xylem = transports water and minerals (generally in the middle) More Structures Phloem = transports sugars to all cells, located outside the xylem Vascular cambium = separates the X and P, contains new cells for vascular growth Pith = central portion of stem of tree, for storage E. Reproduce Without Water Spores/Cones/Seed-protective coat which prevents a developing embryo from drying out Advent of pollen and seeds make it possible to reproduce far away from water Pollen = plant sperm, light weight and won’t dry out, carried via wind, water, animal, etc Pollen Images via SEM