Greenhouse Guide 2014
Total Page：16
File Type：pdf, Size：1020Kb
Student Name______________________Student Number___________________ Biol 441, 20 points BOTANY GREENHOUSE SELF TOUR This is a self-guided tour of the greenhouses, with a focus on angiosperms. As you go through the various rooms and look at the plants, read the information carefully and answer the questions in each section. Due on or before the last lab period. ROOM 2. LYCOPHYTES: Homosporous lycopods: Huperzia Huperzia are characterized by their equal dichotomizing branching patterns in their shoots, strobili, and roots. The epiphytic tropical species have stomata situated exclusively on the adaxial surface of the leaf (unlike many other plants which have the majority of their stomata situated on the abaxial surface of the leaf). This stomatal arrangement is an adaptation for curtailing water loss, since these tropical epiphytic Huperzia have leaves borne on pendant branches, their abaxial surface is exposed to the sun while the adaxial surface is in the shade Epiphytic Huperzia can achieve very large sizes (with some such as H. goebellii producing hanging branches over 20 ft long!). These plants don’t bear strobili on stalks but the sporangia are typically aggregated towards the branch tips. Some species appear to show adaptations for growing in drier climates: H. goebellii has a thick waxy cuticle that gives it its chalky blue color. Heterosporous lycopods: Selaginella and Isoetes Selaginella is a huge genus containing several hundred species. This is a particularly ancient genus of vascular plants, with fossils of plants almost indistinguishable from modern species occurring in coal swamp deposits from the mid Carboniferous (over 300 million years ago!) Selaginella have no true roots, but instead have highly specialized stilt-like branching systems called “rhizophores.” In addition, Selaginella have independently evolved vessels similar to those in Angiosperms and perhaps most surprisingly two species have also evolved true megaphyllous leaves with reticulate venation very similar to the leaves of angiosperms. Most Selaginella spp. are tropical understory plants. Strobili often occur on the tips of the branches. Another group (e.g. S. wallacei and S. peruviana) are true ‘resurrection plants’ adapted to living in seasonally dry environments such as the dry slopes of the Eastern Cascades. During the dry season, the plant shrivels up to conserve moisture, appearing dead. When the rainy season comes, the plants quickly bounce ‘back to life,’ opening up their foliage and sending out new branches and roots. S. oregana is native to the Pacific Northwest and is among the only truly epiphytic Selaginella species in the world. These plants are similar to the resurrection plants in that they have to persist through dry seasons. During the wet season, however, this species has an incredible emerald-green hue. This color festooned atop the hanging moss mats in the Hoh Rainforest is actually what gives the “Hall of Mosses” in Olympic National Park its unusual vibrance: not the mosses but a vascular plant! 1 Student Name______________________Student Number___________________ Isoetes spp. in small tank: Isoetes encompasses the last descendants of an ancient lycopsid lineage that included the gigantic arborescent members that once dominated vast stands of equatorial wetlands during the Carboniferous. The extinct relatives of Isoetes (the Lepidodendrales) make up the vast majority of the world’s coal reserves. Plants in this genus lack true roots. Instead, they have subterranean branches used to uptake carbon dioxide from water-logged soils and undergo respiration. The quill-like leaves of Isoetes lack stomata when the plant grows underwater. These plants use an entirely novel photosynthetic pathway underwater: the Lycopsid Photosynthetic Pathway (LPP), but when growing out of the water, they lose their leaves and grow out new ones with stomata, facultatively switching to C3 photosynthesis. FERNS: Check out the huge specimen of Angiopteris (a Marattioid fern with synangia) and several other smaller ferns. GYMNOSPERMS: Cycads, look for male and female cones (in separate plants). Are sporophylls leaf-like or arranged into a cone? ANGIOSPERMS: CARNIVOROUS PLANTS. One example of the extreme "versatility" of angiosperms in comparison with gymnosperms is the adaptation to carnivory. Most of these plants grow in bogs where there is very little nitrogen available. Eating insects is a way to obtain nitrogen. Sarracenia and Darlingtonia sp. (pitcher plants). The leaves of pitcher plants are shaped as cylindrical containers. Can you speculate on how they got that way from a developmental standpoint? (think of genes involved in leaf development)_______________________________ _____________________________________________________________________________ The leaves have stiff rims that keep them open. In Sarracenia there are also nectaries on the rim to attract visitors. Insects are led downward by additional nectaries inside the pitcher, or they slip on the waxy rim and fall in. They have difficulty crawling out because of stiff downward-pointing hairs on the pitcher walls. Look in the larger pitchers and you can see these hairs. The pitchers contain a solution with digestive enzymes. The flaps that close the pitcher mouths presumably function to keep excessive rain water out. Dionaea sp. (Venus fly traps). Insects crawling on the leaf surface contact trigger hairs (you can see the hairs readily without a hand lens). Osmotic changes are triggered in glands at the base of the leaf, causing the leaves to snap shut. Cells of the leaf begin to secrete digestive enzymes. Drosera sp. Several species of these “sundews” are common in the bogs of the Olympic Peninsula. If you’ve ever hiked from Lake Ozette out to the beach, as you pass through the grassy meadows en route - look for them. Notice that the leaf blades are covered with long hairs having gummy secretions at their tips. Insects get stuck in these secretions and their struggles trigger the hairs to begin bending toward the leaf surface where they are digested by hydrolytic enzymes. What layer of leaf cells likely produces the glandular hairs? _________________________________________________________________ 2 Student Name______________________Student Number___________________ What type of cell is likely responsible for the secretion of digestive enzymes? _________________________________________________________________ OTHER PLANTS OF INTEREST IN ROOM 2 Austrobaileya, is considered a basal angiosperm, belonging in the ANITA grade. Austrobaileya scandens (Austrobaileyaceae, Magnoliales). This is a small, monotypic family known only from northeastern Australia. If flowers are present, with a hand lens you can see the broad, flat stamens lacking differentiation into filament and anther (laminar stamens). Stamens of this type have been hypothesized to represent the ancestral precursor of modern stamens. Woody Magnoliids: Chloranthus sp. The flowers resemble those of flower fossil about 115 million years old; they are very simple, lacking a perianth and style. Drimys winteri can now be found outside (ask for assistance if interested). This genus is in the Winteraceae, a family with many features that may be ancestral (basal), including the absence of vessels. Houttuynia sp. The inflorescence and flowers are similar to the Chloranthaceae. List three features of the above three genera that might be considered ancestral in angiosperms __________________ ___________________ _____________________ MONOCOTS. With rare exceptions, monocots lack secondary growth, a fact that has definite morphological consequences. A large above ground axis is hard to support in the absence of wood. Therefore, branching is suppressed in many monocot species. In those species that do branch, growth is usually sympodial. Each shoot has a limited growth period and then forms terminal flowers. Further vegetative growth on that axis comes from lateral buds - usually located near the base of the flowering stalk. By branching at the base of the plant, new shoots can readily establish contact with the soil by means of adventitious roots. In those species that do exhibit vegetative branching well above the soil surface, branches are usually of very limited diameter, or gain support by climbing or by producing prop roots. Bamboo. Observe the "woody" bamboo, Bambusa oldhamii or giant timber bamboo. Similar type of bamboo is used for making the stakes out in the greenhouse hallway - used in pots to prop up other plants. Bamboos are referred to in the textbooks as "woody" grasses. But this is loose terminology, since no monocot has a dicot-type vascular cambium that produces secondary xylem (wood). What kinds of cells make up the tough "wood" of bamboo stems _____________? Like other grasses, bamboo stems are heavily impregnated with silica. This increases the hardness of the "wood". These stems grow at a rate of about 3 feet/day. Name a morphological feature of bamboos that would indicate that they are monocots ___________________________________________________________________. Orchids. All the orchids in this room are tropical epiphytes (terrestrial orchids are found mostly in temperate zones and are common in WA). There are also orchids in Rm. 5. This room is kept cooler because these particular orchids are native to higher elevations. The Orchidaceae is the largest flowering plant family. About 25,000 species have been described, but doubtless many remain to be discovered. Most are adapted to a particular insect 3 Student Name______________________Student