CMG GardenNotes #134 Plant Structures: Leaves

Transcription

1 CMG GardenNtes #134 Plant Structures: Leaves Outline: Functin, page 1 Structure, page 2 External features, page 3 Leaf arrangement n stem, page 2 Leaf type, page 3 Overall leaf shape, page 3 Shape f leaf r leaflet apex, page 4 Shape f leaf base, page 5 Leaf margins, page 5 Cnifer and Ginkg leaves, page 6 Leaf venatin, page 7 Mdified leaves, page 7 Internal features, page 8 Thught questin: (Explain the science behind the questin.) Last spring my tulips were beautiful. As the plants faded, I remved the blssms and fliage s it wuldn t detract frm the landscape.this year, mst f the tulips didn t grw back. Why? Leaves are the principle structure, prduced n stems, where phtsynthesis takes place. Cacti are an exceptin. The leaves are reduced t spines, and the thick green, fleshy stems are where phtsynthesis takes place. Functins T cmpete fr light fr phtsynthesis (the manufacture f sugars). Evaptranspiratin frm the leaves t mve water and nutrients up frm the rts. Regulate misture, gas exchange and temperature thrugh small penings n the leaf, knwn as stmata. Hrticultural uses Aesthetic qualities Feed and fd Mulch and cmpst Plant identificatin 134-1

2 Prpagatin frm cuttings Summer cling (Evaprative cling accunts fr 70-80% f the shading impact f a tree.) Wildlife habitat Wind, dust and nise reductin Structure External Features Leaf blade Flattened part f the leaf Petile Leaf stalk Stipules Leaf-like appendages at the base f the leaf. Figure 2. External Features f a Leaf Fr plant identificatin purpses, the shape f the leaf margin, leaf tip and leaf base are key features t nte. Remember, a leaf begins at the lateral r auxiliary bud. Leaf Arrangement n Stems Alternate Arranged in staggered fashin alng stem (willw) Oppsite Pair f leaves arranged acrss frm each ther n stem (maple) Whrled Arranged in a ring (catalpa) Rsette Spiral cluster f leaves arranged at the base (r crwn) (dandelin) Figure 3. Leaf Arrangement n Stem 134-2

3 Leaf Type Simple Leaf blade is ne cntinuus unit (cherry, maple, and elm). Cmpund Several leaflets arise frm the same petile. Palmately cmpund Leaflets radiate frm ne central pint (Ohi buckeye and hrse chestnut). Pinnately cmpund Leaflets arranged n bth sides f a cmmn rachis (leaf stalk), like a feather (muntain ash) Bi-pinnately (dubly) cmpund Duble set f cmpund leaflets. Figure 3. Leaf Types Nte: Smetimes identifying a "leaf" r "leaflet" can be cnfusing. Lk at the petile attachment. A leaf petile attaches t the stem at a bud nde. There is n bud nde where leaflets attach t the petile. Overall Leaf Shape Leaf shape is a primary tl in plant identificatin. Descriptins ften g int minute detail abut general leaf shape, and the shape f the leaf apex and base. Figure 5 illustrates cmmn shapes as used in the Manual f Wdy Landscape Plants. Figure 5. Leaf Shapes 134-3

4 Leaf Shape Descriptins Crdate- heart-shaped Cuneate leaves with small width at base, widening near the tp (think wedge) Elliptical leaves widest in the middle, tapering n bth ends Hastate arrwhead shaped leaves Lancelate leaf is 3x r mre lnger than width and bradest belw the middle Linear- leaves narrw, 4x lnger than width and have the same width Obcrdate reverse appearance f crdate leaves. (Heart shape is upside dwn) Oblancelate leaf is 3x lnger than wide and bradest abve the middle Oblng leaf is 2-3x as lng as it is wide and has parallel sides Obvate leaf is bradest abve the middle and abut 2x as lng as the width Ovate- leaf is bradest belw the middle and abut 2x as lng as the width (egg shaped) Peltate leaves runded with petile attached under the leaf base Renifrm leaves wider than they are high Spatulate generally narrw leaves widening t a runded shape at the tip Shape f Leaf r Leaflet Apex Shape f the leaf apex (tip) and base is anther tl in plant identificatin. Figures 6 and 7 illustrate cmmn tip and base styles as used in the Manual f Wdy Landscape Plants. Figure 6. Leaf Tip Shapes Leaf Apex Descriptins Acuminate leaf margins frming a terminal angle f less than 45 degrees Acute leaf margins frming a terminal angle f 45 t 90 degrees Cuspidate tip is sharp; lks like 2 curves meeting at the tip Emarginate tips is slightly indented Mucrnate tip ends in a small sharp pint that is actually cntinuatin f leaf midrib Obcrdate upside dwn heart shape Obtuse leaf tip is blunt with an angle greater than 90 degrees Truncate leaf tip appears t be square-like 134-4

5 Shape f Leaf Base Figure 7. Leaf Base Shapes Leaf Base Descriptins Acute base is pinted, having less than a 90 degree angle Auriculate- base has ear-shaped appendages near the petile Crdate- base is heart shaped Hastate- base has pinted, flaring lbes at base Oblique- base has ne side lwer than the ther Runded- circular with n pint Saggitate- lwer lbes f leaf are flded r pinted dwn Leaf Margins The leaf margin is anther tl in plant identificatin. Figure 8 illustrates cmmn margin types as used in the Manual f Wdy Landscape Plants. Figure 8. Leaf Margins 134-5

6 Leaf Margin Descriptins Crenate leaf edge has blunt, runded teeth Dentate- leaf has triangular r tth-like edges Dubly serrate edges with saw like teeth that have even smaller teeth within the larger nes Entire leaf edge is smth Incised leaf margins have deep, irregular teeth Lbed leaf edges are deep and runded Serrate leaf edges are sharp and saw-like (think serrated knife) Serrulate leaf edges with smaller, mre evenly spaced serratins than a serrated leaf Sinuate margins are slightly wavy Undulate very wavy margins Cnifer and Ginkg Leaves Cnifer types Scale-like Mature leaves cmmn n mst junipers and arbrvitae Awl-shaped Juvenile leaves cmmn n sme junipers Linear-shaped Narrw flat needles f spruce, fir, and yews Needle-like The cluster f needles in pines creates a runded shape. Ginkg type Figure 9. Cnifer leaf types Dichtmus venatin Smewhat parallel vein sectins, frming a 'Y', fund in Ginkg trees. [Figure 10] Figure 10. Dichtmus veined Ginkg leaf 134-6

7 Leaf Venatin Mncts Parallel venatin Veins run in parallel lines (mnct plants, e.g. grasses, lilies, tulips). [Figure 11] Figure 11. Parallel veined mnct leaf Dicts Net-veined r reticulate-veined Leaves with veins that branch frm the main rib and then subdivide int finer veinlets (dict plants). [Figure 12] Pinnate venatin Veins extend frm a midrib t the edge (elm, peach, apple, cherry). Palmate venatin Veins radiate fan-shaped frm the petile (maple, grapes). Figure 12. Venatin f dict leaves Mdified Leaves Adhesive disc Mdified leaf used as an attachment mechanism. Smetimes referred t as a hldfast (Bstn ivy). Bract Specialized, ften highly clred leaf belw flwer that ften serves t lure pllinatrs (pinsettia, dgwd). Thrn Mdified leaf (barberry, pyracantha). Tendril Mdified sinuus leaf used fr climbing r as an attachment mechanism (Virginia creeper, peas, grapes)

8 Figure 13. Thrns are mdified leaves. Internal Features The leaf blade (flattened part f leaf) is cmpsed f several layers. Epidermis Outer layer f tissues Cuticle Waxy prtective uter layer f epidermis that prevents water lss frm leaves, green stems, and fruits. The amunt f cutin r wax increases with light intensity. Leaf hairs Part f the epidermis Vascular bundle Xylem and phlem tissues, cmmnly knwn as leaf veins. Stmates (Stmata) Natural penings in leaves and herbaceus stems that allw fr gas exchange (water vapr, carbn dixide and xygen) and plant cling. Guard cells Specialized kidney-shaped cells that pen and clse the stmata. Figure 1. Leaf Crss Sectinal View with Stmates

9 Additinal Infrmatin CMG GardenNtes n Btany: #121 Hrticulture Classificatin Terms #136 Plant Structures: Fruit #122 Taxnmic Classificatin #137 Plant Structures: Seeds #131 Plant Structures: Cells, Tissues, #141 Plant Grwth Factrs: Phtsynthesis, and Structures Respiratin and Transpiratin #132 Plant Structures: Rts #142 Plant Grwth Factrs: Light #133 Plant Structures: Stems #143 Plant Grwth Factrs: Temperature #134 Plant Structures: Leaves #144 Plant Grwth Factrs: Water #135 Plant Structures: Flwers #145 Plant Grwth Factrs: Hrmnes Authrs: David Whiting, Cnsumer Hrticulture Specialist (retired), Clrad State University Extensin; with Michael Rll and Larry Vickerman (frmer CSU Extensin emplyees). Line drawings by Sctt Jhnsn and David Whiting. Revised by Patti O Neal, Rberta Tlan and Mary Small, CSU Extensin. Clrad Master Gardener GardenNtes are available nline at Clrad State University, U.S. Department f Agriculture and Clrad cunties cperating. Extensin prgrams are available t all withut discriminatin. N endrsement f prducts mentined is intended nr is criticism implied f prducts nt mentined. Cpyright Clrad State University Extensin. All Rights Reserved. CMG GardenNtes may be reprduced, withut change r additins, fr nnprfit educatinal use. Revised Octber