Monday, Week 11 Announcements: NO LAB TODAY. LECTURE: Seed Plants and Angiosperm evolution WEB READING Gymnospermous plants (see pdf of powerpoint for more details) Land Plant Relationships Why is the Angiosperm clade so BIG? Origin of Angiosperms Earliest Fossil Evidence 140 mya Archaefructus - series of conduplicate carpels borne spirally on an elongate axis 130 mya monosulcate pollen 127 mya morphology in Engalnd and W. Africa 120 mya tricolpate pollen 115 mya dicot leaves in N. America 108 mya flowers and wood 75 mya many modern families and genera present So, suddenly in the late Cretaceous (overnight, geologically speaking!), in a landscape dominated by lycopods, ferns, and gymnosperms, there is a huge RADIATION (rapid diversification, on a geological time scale) of flowering plants. This is similar to the socalled Cambrian Explosion for animals (all of the existing animal phyla appear in the fossil record within 10-20 million years at the beginning of the Cambrian). Compared to the 4.5 billion years of evolution on Earth, that s rapid! Today: ~300,000 spp of angiosperms, but fewer than 15,000 spp of gymnosperms. This sudden rise to dominance has mystified scientists for a long time. Darwin, in a letter to a friend, called this an abominable mystery! He was referring to the lack of fossil evidence that would help link angiosperms to other extant or extinct groups. The lack of fossils was attributed to the thought that angiosperms arose in dry, upland areas that were not optimal for fossilization. Darwin's mystery remains even today! Nobody knows what the angiosperm ancestor looked like, but we do know that angiosperms are monophyletic (evolved from a single, common ancestor) both from morphological and molecular phylogenetic studies. Monophyletic origin of angiosperms. Evidence (i.e., angiosperm synapomorphies): 1) Carpel (ovary) enclosing the ovules 2) Bitegmic Ovules (two integuments) 3) Triploid endosperm product of double fertilization 4) Sieve tubes in their phloem to conduct fluids from leaves to other parts of plants Sieve tubes have open ends and stack like straws inside the plant 5) Reduced female gametophytes (usually 7 cells, 8 nucleii) 60
Wednesday, Week 11 Announcements: Vegetative and Reproductive morphology terminology for angiosperms today lots of terms! Short quiz next Wednesday on Vegetative Morphology terminology! LECTURE: Vegetative and Reproductive Morphology Plant Morphology - form or structure of a plant and its parts Vegetative morphology - any portion of a plant that is involved in growth, development, photosynthesis, support, etc., but NOT involved with sexual reproduction. Example: roots, stems, leaves, seeds, etc. Stems At the tip of the growing shoot is a terminal bud or apical bud. A bud has bud scales surrounding it to protect the developing parts inside. Inside a bud are leaf primordia, lateral bud primordia, and the apical meristem. The apical meristem is responsible for new terminal growth. Below the terminal bud regions of the stem may be identified as follows: node - point of attachment of a leaf lateral bud - always found in the axil of a leaf (between the leaf and stem, upward on the stem from the point of attachment of the leaf) internode - region of the stem between two nodes. OTHER STEM FEATURES lenticel raised corky area on stem pith the spongy central tissue in some stems leaf scar bundle scar Leaves At the point of attachment of the stem to the leaf there sometimes is a small leaf-like structure attached to the stem called a stipule a pair of appendages at the base of the leaf, occasionally fused, sometimes falling off soon after leaf develops. Stipules (presence/absence) is often diagnostic. Leaf structure: blade - the broad part of the leaf petiole - the slender part of the leaf that attaches the blade to the stem margin - the edge of the blade; may be smooth or variously shaped (show shapes and briefly go over) ribs - vascular bundles or veins in the leaf; the central one is the midrib 61
Venation (arrangement of veins) - net veined - a branching, divergent and often reticulate pattern may be palmate or pinnate - parallel veined - primary veins all parallel as in grass Leaf Shape: simple - undivided blade compound - blade divided into leaflets, each resembling a leaf; a leaf may be compound more than once. You can tell a compound leaf from a simple leaf, by looking for an axilary bud at the point of attachment of each blade. If you find one, the leaves are simple, if not, they are compound (there should be one at the base of the compound unit, however). dissected, or divided - blade lobed, but not all the way to the midrib. pinnate - arranged like pinnae on a feather palmate - arranged like fingers radiating from the palm of your hand Leaves may be pinnately of palmately compound, however when there are three leaflets it may be impossible to tell which. In that case the leaves are called ternate. Leaf Arrangement (attachment of leaves to stem) Alternate one leaf per node Opposite two leaves per node on opposite side of stem Whorled more than two leaves per node 62
Friday, Week 11 Announcements: Short quiz next Wednesday on Vegetative Morphology terminology! Much like unknowns from lab on Wednesday. Twig keying on Monday in lab twig key at bookstore or print from webpage. LECTURE: Pinus! Pinus monticola western white pine Occupies forests with ample moisture on the Pacific slope and Sierras and disjunct in the northern Rockies. Typically a montane species, but does occur at sea-level on the Olympic Peninsula and British Columbia coast. Intermediate in shade tolerance with Thuja plicata, Tsuga heterophylla, Abies grandis, Larix occidentalis in north and at higher elevations in Sierras with Calocedrus decurrens and Sequoiadendron. 170-180 tall, 2-4 in diameter bark smooth and gray on young trees, forms plates/fissures on old trees to 1.5 thick not fire resistant deep, wide spreading root system leaves persistent 3-4 years, glaucous, blue-green, stomatal lines on inner surfaces. Seed cones 4-10 long, cone scales thin, somewhat reflexed, umbo unarmed, tan apophysis with slightly pointed apex. Seed wings about ½ shorter than scales (this is 1/4' in P. strobus) Severely impacted by white pine blister rust fungus introduces to N. Am. From Eurasia in early 1900 s. Breeding programs to produce resistant strains have been somewhat successful. WPBR affects all 5-needled pines. Pinus strobus eastern white pine Occupies northern deciduous zone occurs (or used to anyway) in mostly pure stands on moderately moist soils. 80-100 tall, 2-3.5 diameter Leaves glaucous, blue-green, fascicles of 5 very similar vegetatively to P. monticola Seed cones 3-8 long cone scales are thin and not reflexed, umbos unarmed with tan apophysis with rounded apex. Seed wings about ¼ shorter than scales (this is 1/2 in P. monticola) Largest of the northeastern conifers and thus, heavily logged throughout range. It is now used extensively to establish new plantations in NE US. Not sister species with P. monticola! Historically used for ship masts one of the primary sources of friction between the colonies and the crown. More resistant to white pine blister rust than P. monticola, but still a problem. 63
Pinus lambertiana sugar pine Occupies sites from 1100-5400 in the southern Cascades and northern Sierras and from 2000-7800 in central and southern Sierra Nevada. Very rarely found in pure stands. This is the largest of all pines discovered by David Douglas. Very fast growing 2 nd only to Sequoiadendron in the Sierra Nevada 100 year old tree may be 140 tall and 3 in diameter may live 500-750 years. 170 to 180, 2-4 diameter largest is >260 and 11.5 in diameter! Bark reddish-brown, composed of scaly ridges separated by fissures up to 4 thick at maturity Leaves glaucous, blue-green, fascicles of 5, stomata on all surfaces. Very similar to western white pine, but needles spirally twisted. Seed cones largest of any pine 11-21. Apophysis somewhat thickened, yellowish brown, diamond shaped, terminal umbo unarmed, with deep seed wells. Named for sweet, sugary sap that flows from bark injuries eaten by Native Americans Pinus flexilis limber pine Occupies dry, rocky slopes and high ridges from the pinyon-juiper zone of the southwestern US all the way to timberline throughout the Rocky mountains. Frequently forms pure stands along the east slope of the northern Rockies and much of the Great Basin, and east slope of the Sierra Nevada. Named for very flexible branches that can be tied in knots. Smaller tree 40-50 tall and 2-3 in diameter on good sites, but often more shrub-like, twisted and contorted at high elevation. May live >1500 years. Bark dark brown and composed of superficially scaly, rectangular plates separated by fissures on mature trees light gray and smooth on young trees. Leaves yellowish-green and stout 2-3.5 long in fascicles of 5, faint stomatal bands. Clumped near tips of branches leaves retained up to 6 years. Seed cones 3-6 long with raised, gold colored apophysis and terminal umbo. Seeds with rudimentary wings or unwinged deep seed wells with no wing scar. Seeds distributed by wildlife especially Clark s nutcracker cache seeds and forget where they all are, so get clumps of individuals together. Ecologically important for controlling soil erosion. OR public broadcasting video of oldest Pinus flexilis in Wallowas http://www.opb.org/programs/ofg/segments/view/1739 64
Pinus albicaulis - whitebark pine Occupies rocky soils on exposed mountain slopes and ridges in the subalpine to timberline. Occurs in small, pure stands. On exposed high elevation sites it often has twisted, crooked, shrub-like form, but may reach 20-50 tall and 1-2 in diameter with a tree-like form at favorable sites see the snag Bark, whitish gray and smooth on young trees, scaly on mature trees Leaves yellowish-green and stout, fascicles of 5, clumped near the tips of limbs. Very similar vegetatively to Pinus flexilis. Seed cones 1.5-3.5 long and serotinous, with very thick cone scales, terminal umbo armed Seeds large, thick walled, wingless. This alpine tree is the only North American representative of the stone pines serotinous species associated with a nutcracker for seed dispersal Clark s nutcracker breaks cones open to get at seeds and leaves cone scales behind forgets where all seeds are cached so get clumps of individuals together. Ecologically important for controlling soil erosion and watershed protection, similar ecological niche as Pinus flexilis. Seeds eaten by native Americans and important food for Black and Grizzly bears. Severely impacted by whitepine blister rust although some resistance has developed. 65