Monocot vs Eudicot

Internal Structure of Stems Vascular bundles of xylem and phloem run through ground tissues of stems, leaves, and roots The bundles conduct water, ions, and nutrients between different parts of the plant, and also function in support vascular bundle Multistranded, sheathed cord of primary xylem and phloem in a stem or leaf

Internal Structure of Stems In herbaceous and young woody eudicot stems, a ring of vascular bundles divides ground tissue into cortex and pith Monocot stems have vascular bundles distributed throughout ground tissue

Primary Structure: Eudicot Stem Just take notice of the arrangement of the Vascular Bundles. This is an Alfalfa plant which is a eudicot. Cortex- located between the vascular bundles and epidermis Pith- located in the center of the stem, surrounded by the vascular bundles. (these structures are unique to Eudicots

Primary Structure: Eudicot Stem A Cross-section of an alfalfa stem. The cylindrical arrangement of vascular bundles is a characteristic of eudicot stems. Figure 25.8 Primary structure of A a eudicot stem and B a monocot stem. Fig. 25.8a.1, p. 402

companion cell in phloem Primary Structure: Eudicot Stem vessel in xylem meristem cell Figure 25.8 Primary structure of A a eudicot stem and B a monocot stem. sieve tube in phloem companion cell in phloem Fig. 25.8a.3, p. 402

Primary Structure: Monocot Stem Just take notice of the arrangement of the Vascular Bundles. This is a Corn stem which is a monocot.

Primary Structure: Monocot Stem B Cross-section of a corn stem. The vascular bundles in monocot stems are not arranged in a cylinder. Figure 25.8 Primary structure of A a eudicot stem and B a monocot stem. Fig. 25.8b.1, p. 402

collenchyma sheath cell companion cell in phloem Primary Structure: Monocot Stem collenchyma sheath cell air space vessel in xylem Figure 25.8 Primary structure of A a eudicot stem and B a monocot stem. sieve tube in phloem companion cell in phloem Fig. 25.8b.3, p. 402

Primary Growth of a Stem Most primary growth occurs by cell divisions of apical meristem in terminal buds (naked or encased in bud scales) Meristem cells differentiate into dermal tissues, primary vascular tissues, and ground tissues A lateral bud is a dormant shoot that forms in a leaf axil Lateral buds give rise to branches, leaves, and flowers

Primary Stem Growth (Eudicot) This is showing how the growth of the stem is equivalent to the elongation and differentiation of cells. Thus, one region eventually becomes differentiated and will appear as if it’s a totally different region after growth has occurred.

Primary Stem Growth (Eudicot) immature leaf apical meristem A Shoot tip, tangential cut. B Same tissue region later, after the shoot tip has lengthened above it. Figure 25.9 Growth in the stem of Coleus, a eudicot. A–C Successive stages of this stem’s primary growth. D The micrograph shows a longitudinal cut through the stem’s center. The tiers of leaves in the photograph below it formed in this linear pattern of development. pith xylem phloem cortex C Later still, different lineages of cells are differentiating and forming complex tissues. Fig. 25.9a-c, p. 403

Leaf Growth

Leaf Development A Shoot tip, tangential cut. immature leaf apical meristem pith vascular tissues forming lateral bud forming epidermis forming apical meristem youngest immature leaf immature leaf B Same tissue region later, after the shoot tip has lengthened above it. C Later still, different lineages of cells are differentiating and forming complex tissues. pith cortex phloem xylem Growth in the stem of Coleus, a eudicot. A–C Successive stages of this stem’s primary growth.

A Closer Look at Leaves Leaves are metabolic factories where photosynthetic cells make sugars Leaves vary in size, shape, surface specializations, and internal structure

Similarities and Differences Leaf shapes and orientations are adaptations that help a plant intercept sunlight and exchange gases. A typical leaf has a flat blade and, in eudicots, a petiole (stalk) attached to the stem Leaves of grasses and other monocots are flat blades, with a base that forms a sheath around the stem Simple leaves are undivided; compound leaves have blades divided as leaflets

Leaf Forms: Eudicots and Monocots petiole axillary bud blade node sheath blade stem Common leaf forms of A eudicots and B monocots node A B Fig. 25.10ab, p. 404

Simple and Compound Leaves elliptic palmate lobed pinnatisect C simple leaves and D compound leaves D acuminate odd pinnate elliptic odd pinnate lobed odd bipinnate Fig. 25.10cd, p. 404

Fine Structure Leaves contain mesophyll and vascular bundles between their upper and lower epidermis A leaf’s internal structure is adapted to intercept sunlight and to enhance gas exchange Many leaves also have surface specializations

Leaf Cell Surface Specialization Hairs on a tomato leaf: Lobed heads are glandular structures that secrete aromatic chemicals that deter plant-eating insects Example of leaf cell surface specialization: hairs on a tomato leaf. The lobed heads are glandular structures that occur on the leaves of many plants; they secrete aromatic chemicals that deter plant-eating insects. Those on marijuana plants secrete the psychoactive chemical tetrahydrocannabinol (THC).

Epidermis Epidermis covers every leaf surface exposed to air A translucent, waxy secreted cuticle slows water loss from the sheet-like array of epidermal cells Water vapor and gases cross the epidermis at stomata Shape changes of guard cells close stomata to prevent water loss, or open stomata to allow gases to cross

Mesophyll Mesophyll consists of photosynthetic parenchyma with air spaces between cells that allow gas exchange Plasmodesmata connect the cytoplasm of adjacent cells In leaves oriented perpendicular to the sun, mesophyll is arranged in two layers: palisade and spongy mesophyll Monocot leaves that grow vertically intercept light from all directions; their mesophyll is not divided into two layers

Veins: The Leaf’s Vascular Bundles Leaf veins are vascular bundles of xylem and phloem, typically strengthened with fibers In eudicots, large veins branch into a network of minor veins embedded in mesophyll; in monocots, veins are similar in length and run parallel with the leaf’s long axis vein A vascular bundle in the stem or leaf of a plant

Eudicot and Monocot Leaves

Anatomy of a Eudicot leaf 1 epidermis palisade mesophyll 3 4 spongy mesophyll xylem 5 vascular tissue phloem stomata 2 Anatomy of a eudicot leaf Fig. 25.12, p. 405