海大植物生物學(xué)課件chapter6the shoot

1、Chapter 6 The Shoot: Primary Structure and DevelopmentOrigin and Growth of the Primary Tissues of the Stem Primary Structure of the Stem Relation between the Vascular Tissues of the Stem and the Leaf Morphology of the Leaf Structure of the Leaf Grass Leaves Leaf AbscissionStem and Leaf Modifications

2、 A portion of a Croton（巴豆） shoot. The leaves of Croton, a eudicot, have a mottled appearance due to clonal variations in the ability of leaf cells to produce chlorophyll and are spirally arranged along the stem. At the apex the leaves are so close together that nodes and internodes are not distingui

3、shable as separate regions of the stem. Growth in length of the stem between successive leaves, which are attached to the stem at the nodes, results in formation of the internodes.Origin and Growth of the Primary Tissues of the Stem Longitudinal section of shoot tip of the common houseplant Coleus b

4、lumei（錦紫蘇）, a eudicot. The leaves in Coleus are arranged opposite one another at the nodes, each successive pair at right angles to the previous pair (decussate phyllotaxy); thus the leaves of the labeled node are at right angles to the plane of section. The apical meristem at the tip of the shoot i

5、s protected by young leaves that fold over it, as seen in this longitudinal section of a eudicot shoot. Activity of the apical meristem, which repetitively produces leaf and bud primordia, results in a succession of repeated units called phytomeres. Each phytomere consists of a node with its attache

6、d leaf, the internode below that leaf, and the bud at the base of the internode. The boundaries of the phytomeres are indicated by the dashed lines. Note that the internodes are of increasing length the farther they are from the apical meristem. Internodal elongation accounts for most of the increas

7、e in length of the stem. Tunica-corpus organization. (a), (b) Detail of a Coleus blumei（錦紫蘇） shoot apex. Coleus has a two-layered tunica, represented by the L1 and L2 layers of the apical meristem. The initial layer of the corpus is represented by the L3 layer. The corpus corresponds to the central

8、mother cell zone. (c) Anticlinal and periclinal divisions. Cell divisions in the tunica layers are almost exclusively anticlinal. Those in the initial layer of the corpus are both anticlinal and periclinal. By dividing periclinally, the cells of the initial layer of the corpus add cells to the corpu

9、s.acb Diagrammatic representation of the anatomy of the top, or crown, of a thick-stemmed monocot without secondary growth, such as a palm tree. Increase in thickness is due to meristematic activity below the young leaf bases. The apical meristem and youngest leaf primordia are conventional in size,

10、 although they appear sunken below broad stem tissues. The zone of procambium formation is called the meristematic cap.Stages in growth of the terminal bud and two lateral buds of the horse chestnut (Aesculus hippocastanum，歐洲七葉樹).(a) The young shoots are tightly packed in the buds and are protected

11、by bud scales, which are highly modified leaves initiated late in the previous growing season. (b) The buds open to reveal the oldest rudimentary leaves .(c) Internodal elongation has separated the nodes from one another. The terminal bud of the horse chestnut is a mixed bud, containing both leaves

12、and flowers, although the flowers are not visible here. The lateral buds produce only leaves. Stem with buds and 3-year old shoot with buds Primary Structure of the Stem Considerable variation exists in the primary structure of stems of seed plants, but three basic types of organization can be recog

13、nized: The vascular system of the internode appears as a more or less continuous cylinder within the ground tissue(conifers, magnoliids, and eudicots).The primary vascular tissues develop as a cylinder of discrete strands, or bundles, separated from one another by ground tissue.In the stems of most

14、monocots and of some herbaceous eudicots, the vascular bundles occurs in more than one ring of bundles or appear scattered throughout the ground tissue. The three basic types of organization in primary structure of stems as seen in transverse section. (a) The vascular system appears as a continuous

15、hollow cylinder around the pith. (b) Discrete vascular bundles form a single ring around the pith. (c) The vascular bundles appear scattered throughout the ground tissue.The primary vascular tissues of the Tilia stem form an almost continuous vascular cylinderTransverse section of basswood (Tilia am

16、ericana) stem in a primary stage of growth. The vascular tissues appear as a continuous hollow cylinder that divides the ground tissue into pith and cortex. Detail of a portion of the same basswood stem. The primary vascular tissues of the Sambucus stem form a system of discrete strands Transverse s

17、ections of the stem of the elderberry (Sambucus canadensis)（接骨木） in a primary stage of growth. (a) A very young stem, showing protoderm, ground meristem, and three discrete procambial strands. The procambial strand on the left contains one mature sieve element (upper arrow) and one mature tracheary

18、element (lower arrow). Transverse sections of the stem of the elderberry (Sambucus canadensis) in a primary stage of growth. (b) Primary tissues farther along in development. Transverse sections of the stem of the elderberry (Sambucus canadensis) in a primary stage of growth. (c) Stem near completio

19、n of primary growth. Fascicular and interfascicular cambia are not yet formed. The stems of Medicago and Ranunculus are herbaceous Transverse section of stem of alfalfa(Medicago sativa)（苜蓿）, a eudicot with discrete vascular bundles(middle) and detail of a portion of the same alfalfa stem(right) A cl

20、osed vascular bundle. Transverse section of vascular bundle of the buttercup (Ranunculus)（毛茛）, an herbaceous eudicot. The vascular bundles of the buttercup are closed, that is, all of the procambial cells mature, precluding secondary growth. The primary phloem and primary xylem are surrounded by a b

21、undle sheath of thick-walled sclerenchyma cells. In the Zea stem the vascular bundles appear scattered in transverse section Stem of maize (Zea mays). (a) Transverse section of the internodal region, showing numerous vascular bundles scattered throughout the ground tissue. (b) Transverse section of

22、the nodal region of a young maize stem, showing horizontal procambial strands that interconnect the vertical bundles. (c) A mature stem split longitudinally; the ground tissue has been removed to expose the vascular system. Three stages in the differentiation of the vascular bundles of maize (Zea ma

23、ys), as seen in transverse sections of the stem. (a) The protophloem elements and two protoxylem elements are mature. Three stages in the differentiation of the vascular bundles of maize (Zea mays), as seen in transverse sections of the stem. (b) The protophloem sieve elements are now crushed, and m

24、uch of the metaphloem is mature. Three protoxylem elements are now mature, and the two metaxylem vessel elements are almost fully expanded. Three stages in the differentiation of the vascular bundles of maize (Zea mays), as seen in transverse sections of the stem. (c) Mature vascular bundle surround

25、ed by a sheath of thick-walled sclerenchyma cells. The metaphloem is composed entirely of sieve-tube elements and companion cells. The portion of the vascular bundle once occupied by the protoxylem elements is now a large space known as the protoxylem lacuna. Note the wall thickenings of destroyed p

26、rotoxylem elements bordering the air space. Diagrams of the primary vascular system in the stem of an elm (Ulmus)（榆樹）, a eudicot. (a) A transverse section of the stem showing the discrete vascular bundles encircling the pith. (b) Longitudinal view showing the vascular cylinder as though cut through

27、leaf trace 5 in (a) and spread out in one plane. The transverse section in (a) corresponds with the topmost view in (b). The numbers in both views indicate leaf traces. Three leaf traces-a median trace and two lateral traces-connect the vascular system of the stem with that of the leaf. A stem bundl

28、e and its associated leaf traces are called a sympodiumRelation between the vascular tissues of the stem and the leaf The relation between branch traces and a leaf trace to the vascular system in the main stem. Actually, the branch traces are leaf traces-the leaf traces of the first leaves of the bu

29、d or lateral branch. In magnoliids and eudicots, there are ordinarily two branch traces per bud.Morphology of the Leaf1. Simple Leaf: One Blade 2. Compound Leaf: Blade Divided Into Leaflets A. Palmately Compound leaf: No RachisMarijuana （Cannabis sativa 大麻）Aesculus chinensis (七葉樹） with Palmately Com

30、pound leafAesculus turbinata (日本七葉樹）with Palmately Compound leafB. Pinnately Compound (Pinnate): With A Rachis Arachia hypogaea (落花生) with even pinnately compound leaf Caesalpinia decapetala (云實(shí)）with even pinnately compound leafBlack locust (Robinia pseudoacacia, 刺槐) Odd Pinnately Compound leaf C. P

31、innately and Palmately Trifoliate Left: basket bush (Rhus trilobata)(漆樹）; Center: poison oak (Toxicodendron diversilobum)（毒葛）; Right: Baja California poison ivy (T. radicans ssp. divaricatum)（常春藤）. Rhus trilobata (漆樹）Lespedeza bicolor (胡枝子）with ternate pinnate leafD. Twice Pinnate Compound leaf (Bip

32、innate) Albizia julibrissin (合歡） with twice Pinnate Compound leaf E. Pinnatid: Pinnately Dissected Nearly To The MidribPolypodium sp. with pinnatifid leafThe Hawaiian tree fern (Cibotium glaucum) in Hawaii Volcanoes National Park on the island of Hawaii. These beautiful native ferns form a dominant

33、understory component in forests of ohia (Metrosideros polymorpha). Sadlera cyatheoides, an endemic Hawaiian fern that commonly grows on lava flows around Kilauea Crater. On the underside of the smallest leaf divisions (pinnules) is a brown linear sorus (sporangia cluster). This fern is one of the fi

34、rst plants to colonize lava flows after an eruption.3. Leaf Arrangement (Phyllotaxy) Three different leaf arrangements: Alternate (one leaf per node), opposite (two leaves per node) and whorled (three or more leaves per node). A node is the place where one or more leaves are attached along the stem.

35、 The area between the nodes is called the internode.Cinnamomum camphora （樟樹）with alternate leaf arrangementLigustrum lucidum （女貞）with opposite leaf arrangementLilium tsingtauense (青島百合）and Polygonatum sibiricum（黃精） with whorled leaf arrangement.4. Leaf Venation Leaf venation in two species of Ceanot

36、hus leucodermous (白皮美洲茶）has glaucous leaves with three main veins from the base. This is a thorny (spiny) chaparral shrub with rigid, sharp-pointed branchlets. It is common on Palomar Mountain in San Diego County. C. palmeri（帕麥爾氏美洲茶） has pale green leaves with one main vein from the base. This shrub

37、 is also common on Palomar MountainPrunus mume （梅）with pinnate leaf venation.Ricinus communis (蓖麻）with palmate leaf venation. Ginkgo biloba (銀杏） with dichotomous venation.5. Leaf Shapes A. The Prefix Ob In A Descriptive Leaf Term B. Images Of Leaf Shapes 6. Leaf Apices 7. Leaf Bases 8. Leaf Margins

38、The pinnately compound leaf of the pea (Pisum sativum). The pinnately compound leaf of the pea (Pisum sativum). Notice the stipules at the base of the leaf and the slender tendrils at the tip of the leaf. In the pea leaf, the stipules are often larger than the leaflets.Sessile leavesSessile leaves (

39、leaves without a petiole) are often found among eudicots, such as Moricandia, a member of the mustard family (a), but are particularly characteristic of grasses and other monocots. (b) In maize (Zea mays), a monocot, the base of the leaf forms a sheath around the stem. The ligule, a small flap of ti

40、ssue extending upward from the sheath, is visible. The parallel arrangement of the longitudinal veins is conspicuous in the portion of the blade shown here.9.Conifer Leaves Structure of the LeafSections of lilac (Syringa vulgaris)（西洋丁香） leaf. (a) A transverse section through a midrib showing the mid

41、vein. b) A transverse section through a portion of the blade. Two small veins (minor veins) can be seen in this view. Sections of lilac (Syringa vulgaris) leaf. (c) This is a paradermal section of the leaf. Strictly speaking, a paradermal section is one cut parallel to the epidermis. In practice, su

42、ch sections are more or less oblique and extend from the upper to the lower epidermis. Sections of lilac (Syringa vulgaris) leaf. (d), (e) Enlargements of portions of (c). (d) Palisade parenchyma and spongy parenchyma with a vein ending, sectioned through some tracheary elements and surrounded by a

43、bundle sheath. (e) A portion of the lower epidermis with two trichomes (epidermal hairs) and several stomata.Transverse section of a leaf of the water lily (Nymphaea odorata), a magnoliid, which floats on the surface of the water and has stomata in the upper epidermis only. As is typical of hydrophy

44、tes, the vascular tissue in the Nymphaea leaf is much reduced, especially the xylem. The palisade parenchyma consists of several layers of cells above the spongy parenchyma. Note the large intercellular (air) spaces, which add buoyancy to this floating leaf.Transverse section of oleander(Nerium olea

45、nder)(歐洲夾竹桃） leaf. Oleander is a xerophyte, and this is reflected in the structure of leaf. Note the very thick cuticle covering the multiple(several-layered) epidermis on the upper and lower surfaces of the leaf. The stomata and trichomes are restricted to invaginated portions of the lower epidermi

46、s called stomatal crypts.The leaf surface of a species of Tradescantia(紫露草）, also known as spiderwort (Commelinaceae)。 Note the paired guard cells and stoma (opening slit) between them (circled in red). Also note the scattered hairs (trichomes).Microscopic view of the paired guard cells and stoma on

47、 the leaf surface of spiderwort (Tradescantia). An opening or stoma develops between the inflated (turgid) guard cells due to a differential thickening of their walls.Stomatal crypt. Scanning electron micrographs of a stomatal crypt in the lower epidermis of an oleander (Nerium oleander)（夾竹桃） leaf.

48、(a) Lower-magnification view of a crypt, showing numerous trichomes lining the crypt. (b) A higher magnification showing one of the stomata (arrow), which are restricted to crypts.Stomata, shown in scanning electron micrographs. (a) Potato (Solanum tuberosum) leaf, showing the random arrangement of

49、stomata typical of the leaves of eudicots. The guard cells in potato are crescent-shaped and are not associated with subsidiary cells. (b) Maize (Zea mays) leaf, showing the parallel arrangement of stomata typical of the leaves of monocots. In maize each pair of narrow guard cells is associated with

50、 two subsidiary cells, one on each side of the stoma.Grass LeavesTransverse section of sugarcane (Saccharum officinarum) leaf. As is typical of C4 grasses, the mesophyll cells (arrows) are radially arranged around the bundle sheaths, which consist of large cells containing many large chloroplasts.Transverse section of wheat (Triticum aestivum) leaf. As is typical of C3 grasses, the mesophyll cells are not radia