Parts of the stem. What does a stem do? Botany for Master Gardeners Part II

Transcription

1 Botany for Master Gardeners Part II Selected plant parts and their reasons for being What you should know by the end of today s session How to tell a stem from a root How to recognize a simple and compound leaf How to describe how water gets to the top of trees How to tell a monocot from a dicot What does a stem do? Physically support leaves, flowers & fruits Transport water, minerals & nutrients Provides storage in some plants Parts of the stem node = place where leaf is (or was) attached to the stem internode = distance between nodes Note: Stem parts are important in plant identification! One year of growth from one bud scar to another terminal bud bud scales axillary or lateral bud leaf scar bud scale scar A closer look at buds node 1

2 lateral bud Let s review leaf scar bud scale scars Lateral or axillary buds Located in the angle where the leaf attaches to the stem Axillary bud may produce lateral shoot or branch Terminal bud apical meristem leaf primordia axillary buds internode node corn What s inside the stem? vascular bundles cortex cells add structural strength to the stem 2

3 phloem on the outside xylem on the inside vascular bundle Notice the positions of the tissues as related to the outer layer of the stem! phloem xylem What does the phloem do? transports nutrients in sap What does the xylem do? transports water and minerals Stem cross-section Herbaceous monocot (corn) phloem xylem Notice the relative position of the xylem and phloem! Herbaceous dicot (clover) Cross-section of stems Herbaceous monocot (corn) Herbaceous dicot (clover) Note: A vascular cambium is between the xylem and phloem in dicots, but not in monocots What else to you notice? A dicot stem has vascular bundles in a ring Stem cross-sections Herbaceous monocot (corn) Woody dicot (maple tree) vascular cambium 3

4 vascular cambium bark vascular cambium phloem xylem phloem xylem bark What s this area? Secondary/Secondary.html Vascular cambium o Cambium is a meristematic tissue, meaning it divides to produce new tissues o Cambium divides to produce oxylem: to the inside (heartwood, pith) o phloem: to the outside (part of bark) o Responsible for girth growth, or increased stem diameter in woody plants? What is bark? Answer. Bark is the outer layer of cells on a tree containing cambium, compressed phloem, and cork Xylem cells? What direction o Carry H 2 O & dissolved nutrients o Cells are: o long, open-ended, connected end to end o have thick cell walls o resemble straws does the xylem transport its materials? Answer: xylem cells transport water and minerals primarily from the soil upwards 4

5 Phloem cells o Transport actively photosynthetic products o from leaves to roots, stems, flowers & fruits o Cells are: o long and tube-like o without extra cell wall thickening? What direction does the phloem transport its materials? Answer: Phloem cells transports nutrients downward, sideways, and even up wherever the plants needs the energy Let s review vascular bundles Vascular bundle Phloem transports photosynthetic products to areas of the plants needing energy Xylem is like tiny straws and transports water and minerals from the soil to other parts of the plant What do roots do? o take up water and minerals o anchor the plant o store food reserves in over-wintering perennials Kinds of root systems o tap root, can be large of narrow o fibrous or lateral roots form a network in the ground 5

6 buttercup What s inside a root?? How does this differ from a stem? Answer: The vascular system is in the center What s inside a root? buttercup xylem cambium in woody roots phloem cortex Unique to roots! root cap - located at root tip & protects growing point Origin of lateral roots root cap Notice the root cap on the lateral root Root hairs, another unique feature? Root hairs delicate thin-walled Root hairs on a radish seedling What is the function of root hairs? Answer: Absorb water and minerals from the soil room for lots of water has lower water pressure than the outside soil caprio/root_hair_bw.j PG 6

7 What do leaves do? o photosynthesize orespire o transpire Major leaf parts lamina (leaf blade) - highly variable in size and shape petiole - stalk at base of leaf that attaches leaf blade to stem Leaf vein patterns Remember monocots & dicots? leaf blade petiole dicots monocot Let s practice Monocot or Dicot?? 7

8 ???? Compound vs. Simple leaves Simple leaf Buds are in the axils between leaf and stem Hint: Where is lateral bud? 8

9 Compound leaves Simple or compound? leaflet pinnately compound palmately compound Where is the bud? leaflet pinnately compound? simple? leaflet palmately compound? pinnately compound? 9

10 Albizzia bipinnately compound What is photosynthesis? Answer. Photosynthesis is the process whereby plant use the energy of light to convert carbon dioxide and water to sugars Sugars produced through photosynthesis are the building blocks of life as we know it What is respiration? In carbon dioxide, water Out sugars oxygen water Answer. Respiration is the opposite of photosynthesis In respiration, sugars, water, and oxygen are used and carbon dioxide and water are released The photosynthesis factory True or False? Only plants photosynthesize and only animals respire Answer: Only plants photosynthesize but both plants & animals respire Epidermis What is the leaf epidermis? Answer: The epidermis is the top and bottom layer of cells on a leaf 10

11 Leaf model What do stomates do? mesophyll open closed Stomates are small pores on the leaf epidermis used for gas exchange What is transpiration? Answer: Transpiration is water loss (as vapor) from a plant Transpiration rate is controlled by opening and closing of the stomates, which is influenced by humidity, temperature, and light Finally! Putting it all together? How does water get from the soil to the top of a tree? The Elements... Root hairs (often with the help of mycorhizzae) absorb water from the soil Xylem cells transport water via capillary action and cohesive force of water Stomates control evaporation which creates a lower pressure in the vascular system Let s review Name three critical processes carried out by leaves Answer: photosynthesis, respiration, and transpiration What role does transpiration play in water movement in plants? Answer: transpiration creates a lower pressure in the vascular system which draws water from the soil 11

12 What do flowers do? oreproduce It s all about sex o if fertilization occurs, seeds are produced and carried in cones (conifers) or fruits (flowering plants) flower It is not always what it seems! Parts of a flower filament style anther stigma Lily Flower parts anther stigma sepal 12

13 Flower Types Complete Has all floral parts present (sepals, petals, stamens, pistils) Incomplete -flower lacks 1 or more of the 4 parts Flower Types, Continued Perfect Has both stamens and pistils (male and female parts) Imperfect Lacks either stamens or pistils Complete or Incomplete? New Question. Perfect or Imperfect? male flower (staminate) begonia female flower (pistillate) begonia Answer: These are imperfect flowers. Perfect flowers have both male and female parts in the same flower Kinds of plants with catkins are usually imperfect. Can you think of more examples? Remember, It s All About Sex! poplar alder 13

14 pollen on sticky surface of stigma Fertilization pollen grains pollen tube ovary ovule Ovary cross-section of ovary The old birds and bees thing Guess the pollinator big leaf maple willow cape fuchsia beetles wind hummingbirds Guess the pollinator yarrow skunk cabbage cat s ear butterflies flies bees 14

15 One More Thing to Learn Question: What is the floral difference between monocots and dicots? Answer: Monocots have flower parts in multiples of 3; Dicots are in multiples of 2, 4 or 5 Summary of differences, monocots & dicots Time to practice with pictures!?? 15

16 ???? Fun Activity? 16

17 Resources Capon B, Botany for gardeners, Timber Press, Portland OR, 220 pp. ISBN (paper). Elpel, Thomas Thomas J Elpel s herbal field guide to plant families, 4 th ed., HOPS Press, Pony, MT, 196 pp. ISBN Resources Resources Baumgardt, John Philip How to identify flowering plant families: a practical guide for horticulturists and plant lovers. Timber Press, Portland, OR, 269 pp. ISBN Web Sources UC Davis U Texas Purdue U OSU UCLA Rutgers U Princeton U Texas A&M U U HI Queens U Charlotte U IL Urbana-Charlotte U AZ U Miami Cleveland St U Wilkes U Acknowledgements U WI Stevens Pt U Florida WSU UC Berkeley CA St U Stanislaus Botanical Soc America Southern IL U U KY U WI Madison IA St U Eastern OR U La Grande U of MD Vanderbilt U MI St U Grand Rapids Comm C Cornell U U CT U Chicago CO St U Ohio St U U NE Lincoln U NM U System GA U North AL Sidwell Friends School Stanford U Texas Tech U Many photographs by Linda R McMahan, OSU Extension, Yamhill County Some slides from an original presentation prepared by Ann Marie VanderZanden Stony Brook U Maricopa Comm C 17