BIOL 3427 1st Edition Lecture 6Outline of Last Lecture I. shoot apical meristemII. three types of organization of primary structure of stemsa. relationship between leaves and stemsb. variations in leaf structureIII. development of flowersIV. modification of stems and leavesCurrent LectureI. Scattered vascular bundlesa. Zea (maize)b. closed vascular bundlesc. similar to eudicot stemsi. same bundle structureii. phloem toward exterior, xylem toward interior iii. protoxylem lacuna 1. space from lacuna iv. Mature bundleII. Relation between the Vascular Tissues of the Stem and the Leafa. procambial system of leaf is continuous with stemb. bundles diverge at each nodec. leaf tracesi. extensions from vascular system in stem towards leavesd. leaf trace gapsi. gaps of ground tissue in vascular cylinder above leaf tracese. pattern of vascular system in stem reflects arrangement of leavesf. branch tracei. connects vascular system of axillary bud to main stemii. branch gap also apparent III. Leaf arrangementa. Phyllotaxyi. helical (spiral)1. 1 leaf/node, spiral patternii. Distichous1. 1 leaf/node, alternating on opposite sidesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iii. Opposite1. 2 leaves/node on opposite sidesiv. decussate (mint family)1. 2 opposite leaves/node, pairs at right angles to each otherv. Whorled1. 3 or more leaves/nodeIV. Morphology of the Leafa. highly variableb. parts of leafi. blade (lamina)ii. petioleiii. sheathc. morphologyi. simpleii. compoundiii. pinnatelyiv. palmatelyd. distinguish leaflets from leavesi. buds are in axils of leaves not of leafletsii. leaves extend in various planes; leaflets in oneV. Structure of the Leafa. Variationi. Habitat1. availability of waterb. characterize plants by water availabilityi. mesophytesii. hydrophytesiii. xerophytesc. specialized for photosynthesisi. all three tissue systems like roots and stemsd. epidermisi. compactly arrangedii. covered with cuticleiii. stomata may occur on one or both sides1. scattered(eudicots, magnoliids)2. arranged in rows (monocots)iv. xerophytes1. may have more stomata2. sunken stomata on lower surface of leavesa. epidermal hairs (trichomas) insidee. mesophylli. ground tissue of leafii. large volume of intercellular spacesiii. numerous chloroplastsiv. mesophytes1. palisade parenchymaa. upper side, columnar, does most photosynthesis in leaf2. spongy parenchymaa. lower side, irregular shapef. vascular bundlesi. netted (reticulate) venation1. branching pattern2. most magnoliids and eudicotsii. parallel venation1. most monocotsiii. veins contain xylem(upper side) and phloem (lower side)iv. minor and major veins1. protected from intercellular spacesa. bundle sheath: compactly arranged cells with casparianstripVI. Grass Leavesa. Epidermisi. Most cells narrow, elongateii. Bulliform cells1. Large “motor cells”2. Participate in folding/unfolding of leaf during water stressVII. Development of the Leafa. Leaf developmenti. Intercalary growth1. Cell division/enlargement throughout the blade2. Causes major leaf expansion3. Tip of leaf stops growing first (from tip to base)ii. Leaves/flowers have determinate growth1. Restricted, unlike indeterminate growth of apical meristemsVIII. clonal analysisa. chimeral meristemsb. genetic mosaicsIX. leaf developmenta. Founder cellsi. In peripheral zone of apical meristemb. Leaf buttressi. Bulge formed by division and expansion of founder cellsc. Leaf primordiumi. Develops as buttresses continue to growX. Magnoliids and eduicot leavesa. Procambium differentiates to become midveinb. Major veins develop upward/outwardc. Minor veins develop from tip to base of bladeXI. Monocot leavesa. Growth spreads laterally and encircles shoot apexb. Then growth proceeds linearly from basal intercalary meristemXII. Sun and Shade Leavesa. Environment can affect leaf size and thicknessb. Sun leavesi. Smaller , thicker than shade leavesii. More extensive vascular systemiii. Epidermal cell walls thickeriv. Higher photosynthetic rates under high lightXIII. Environment can affect leaf size and thickness: a. sun leavesi. smaller, thicker than shade leavesii. more extensive vascular systemiii. epidermal cell walls thickerb. Leaf Abscissioni. Definition1. Normal separation of leaf from stemii. abscission zone1. formed by structural and chemical changes near base of petiole2. woody angiospermsa. separation (abscission) layerb. protective layeri. becomes leaf scariii. retranslocationiv. leaf scarXIV. Transition between Vascular Systems of the Root and Shoota. distinctions between plant organsi. in eudicotsb. transition regionc. Development of the Floweri. sequence of physiological and structural changesii. initiation of flowers similar to initiation of leavesiii. homeotic mutations1. horticulturists2. plant geneticists3. Arabidopsis thalianaa. three classes of genes essential to normal floral developmenti. Class A: apetala2ii. Class B: apetala3 and pistallataiii. Class C: agamousXV. Stem and Leaf Modificationsa. Tendrilsi. aid in supportii. some modified stems1. Boston ivy (Parthenocissus tricuspidata)2. Virginia creeper (Parthenocissus quinquefolia)3. grape (Vitis)iii. most modified leaves1. garden pea (Pisum sativum)b. cladophyllsi. modified stems that appear to be leavesii. do not have buds in axilsiii. asparagus (Asparagus officinalis)iv. some cactic. spinesd. thornse. pricklesf. carnivorous plantsg. tubersh. bulbi. cormj. petiolek. succulent