Lab 2 The reinvasion of flowering plants into aquatic habitats BIOL 3601: PLANT DIVERSITY Lab Goals: To learn about adaptations of aquatic plants in different aquatic zones To learn common aquatic plants of northern Minnesota Thousands of plant species live in freshwater habitats around the world: along edges, on the surface, or at the bottom of shallow lakes and ponds; in temporarily flooded low areas and meadows; at seeps and springs; in flowing water of streams and rivers; rooted in waterlogged soils; and along any other natural or human-produced drainage system. "Freshwater wetlands" occur from below sea level to some very lofty alpine habitats, where water may persist throughout the year or where it can be very ephemeral. Normally we classify a freshwater wetland as a place where at least half of the species found there are truly aquatic plant species. Many species of aquatic plants are essentially cosmopolitan, meaning that they are widely distributed around the world. Some of the widest distributions are attributable to human activities. Humans have accidentally (sometimes intentionally) transported seeds, fruits, or vegetative clones from one pond or watershed to another, but many of the cosmopolitan distributions are attributable instead to birds, particularly waterfowl, which inadvertently transport the plant propagules in their feathers or in mud on their feet. All of the flowering plant species in Minnesota are secondarily aquatic, meaning that they re-invaded water from terrestrial ancestors. There is even speculation that some angiosperm lineages are secondarily terrestrial (evolutionary history: water land water land)! Taxonomists still debate, however, whether the first angiosperms were small aquatic paleoherbs or large and tree-like. The figure below demonstrates how widespread the aquatic habit (indicated by stars) is amongst diverse angiosperm lineages. (coontails)
Ranunculus is an example of a genus with both terrestrial and aquatic species. As a result of secondarily aquatic plants terrestrial evolutionary baggage, they have some unique adaptations for coping with the stresses of the aquatic environment. By the end of the lab period, you should be able to: 1. Describe the most fundamental stresses that aquatic plants experience: 2. Contrast the stomata distribution in submerged, floating-leaf, and emergent plants: 3. Contrast the effect of gravity and adaptations of plants to gravity in emergent vs. submerged plants: 4. Contrast the roles of roots in submerged, floating, and emergent plants:
Exercise 1: Discovering plants on the shore line BIOL 3601: PLANT DIVERSITY AQUATIC ZONES Aquatic plants occur in distinct, although often overlapping zones. These zones include the edge habitats that that little or no standing water, progressively deeper water, and open water. You can observe similar patterns of zonation spatially and temporally. Plants are adapted to the unique conditions at different water depths. These plants also alter their environment over time by, for example trapping of silt in roots and old leaf bases. This raises the level of the land, making it drier and gradually transforming it into an area more suited to a different set of plant species. Today we will be identifying some common species that occur in northern MN wetlands in different aquatic zones. ALONG THE SHORE Types of plants: Adaptations: SHALLOW WATER Types of plants: Adaptations: OPEN WATER Types of plants: Adaptations:
From shore or from water (using chest waders) collect as many species as you can find and bring them back to the dock for identification. Sketch and photograph the species that we have identified. What aquatic zone were they sampled from? You will be expected to learn the common names of these plants and be able to identify them from a photograph in a future ID quiz.
Exercise 2: Plants in different aquatic zones We will tour the region of Rice Lake shown below on the pontoon boat. We will examine species not visible from shore To reinforce the idea that different plant species are adapted to different aquatic zones, draw on your map areas where you can identify particular species. Think about the adaptations these plants have to the habitat in which they occur. You are here Rice Lake