Submitted by Tyler Hardy In this week’s lab, we took a close look at the characters of woody twigs of vascular plants. It may not seem like it initially, but there is a lot going on with these complex pieces of anatomy! These multi-faceted structures play an important role in several different plant functions, including water and nutrient transport, gas exchange, structural integrity, and new growth. Each twig has a variety of different organs present to be able to perform these duties; check it out! First, lets take a glance at a few twigs from different species, then we can break down what we are looking at. At the very tip of a twig, you can find the terminal or apical bud, enclosed within bud scales for protection. This is where the newest growth of this branch or twig happens. You may find similar, smaller structures to the sides of this and along the stem in areas known as axils. These are the axillary buds; from these buds, a plant may develop smaller vegetative or reproductive shoots. Just below each axillary bud, there is the leaf scar (or a leaf, depending on the plant and time of year), on the node where the leaf once was attached to the branch. The spaces between each node are called internodes. Within each leaf scar, notice the very small pores. These are the vascular bundle scars, the remnant of the vascular structures which once ran to and from the leaf. Following a twig lengthwise, you may notice how it maybe segmented by annular rings. These rings are the bud scale scars, what’s left from last year’s apical bud, and the space between each represents one year’s growth. All along the twig, look for small pores called lenticels. These help to provide gas exchange through the thick, protective bark that covers the woody parts of plants. And that’s just on the surface! Inside each twig are layers of protective tissues, photosynthetic tissues, structural tissues, and vascular tissues, all highly organized and intricately connected for maximum efficiency. So, next time you are picking up sticks in your yard, playing fetch with your dog, or just snapping twigs while you idle, try to remember what complex pieces of biological machinery it is that you are handling!
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Submitted by Alexander GettyIn a previous lab, we inoculated petri dishes with Ceratopteris richardii (known as “C-fern”) spores. The C-fern is a species of aquatic fern native to the tropics, and is a popular “model organism” for lab use because it is easily cultured and has a fast life cycle. It is our goal today to find and follow one of the C-fern sperm cells on its journey. It will not be easy; these tiny, multi-flagellate cells are on a mission, moving very rapidly. They do not have much time, maybe 48 hours max to reach their target destination, before the solitary cell consumes all its resources and will die. Will the sperm make it? Will it fulfill its duty, and succeed in its sole purpose of existence? Ferns reproduce by first producing a spore by meiosis. These spores are dispersed, and generate the gametophyte body. The gametophytes of the C-fern may be either male, which are smaller, or hermaphrodite, which are 4-5 times larger and “mitten” shaped. Male gametophytes develop structures called antheridia which produce and disperse sperm cells. Hermaphrodites also have antheridia, but produce and disperse sperm less effectively. Instead, hermaphrodite gametophytes have a second structure called the archegonium, where the egg develops. In contact with water, male antheridia release their flagellate, swimming sperm on an epic journey to locate and penetrate the archegonia of the hermaphrodite C-fern gametophytes. If successful, this will fertilize the egg, and develop into the embryo of a new sporophyte body, which will then produce more spores and start the cycle again. Using a dissecting microscope, we examined our petri dishes and locate a few male and hermaphrodite C-fern gametophyte bodies. We will then transfer these to a slide with a drop of water for viewing under the compound microscope. The water should cause the male antheridia to release their sperm cells on their journey. The sperm of the C-fern is no easy prey, as I quickly find while trying to capture one on film. Not only are they tiny and quite quick, but they are also more or less translucent. For quite some time you will notice as I attempt to catch one of the sperm being released from the antheridia, with no luck. Some sperm is visible stuck between the gametophyte body and the cover slip, spinning in place, and then at the 3 minute mark we see one sperm break away and set off on a fantastic journey. Spinning around wildly, the sperm swims to and fro while I frantically try to keep it in view and in focus, only to eventually exhaust itself and stop. Ceratopteris richardii “C-fern” gametophyte at 400x magnification, showing first the male body with its antheridia, then eventually a free swimming sperm. Courtesy of Alexander Getty
Oh man finally, I'm off of work. Now I can go to class and sit, I'm so tired of standing. Today's been a long day but now I have botany class! So here we are at lab and today's focus is about recognizing the tissues within stems and their functions, exploring the diversity of plant stems from different habitats, and seeing the difference between a monocot and a dicot plant. We did multiple cross sections of different types of plants. Let me tell you what! Cross sections are not easy. In order to get the best possible result you need to be able to cut the stem very thin. The problem for me is that my hand shakes too much, so it took me a couple tries to get a perfect cross section. One of my best cross sections is the broad bean stem, which can be seen in figure 1. This image was prepared and stained with Toluidine Blue O (TBO), and that's the reason we are able to see different colors and easily distinguish the different structures in this plant stem. The obvious thing you can notice between Figure 1 and Figure 2 is the complexity of a dicot structure. A distinct separation, that looks like a river that cuts through the forest, is called procambium. This separates the pith and the cortex of the stem. Not only that, comparing Figure 1 to Figure 2, their vascular bundle is very different from each other. In figure 1 you can see a separation between the xylem, which is responsible for transporting water and minerals, and the phloem, which is responsible for transporting food to the rest of the plant. But in figure 2 you can see that they're really close together, almost as if they were one. Now if we look closely at figure 1, you can see a blue stain on top of the phloem. That's what they call sclerenchyma, and we were told in class that this acts as a helmet and protects the phloem .
Now lets look at aquatic plants: Figure 3: These are images of a waterweed (Elodea). This is a cross section of its stem, and was stained with TBO. This image was taken under a compound microscope at about 40x. The second image is a zoomed in version of the first image. (Prepared and photographed by Taylor) The plant structure in land plants compared to aquatic plants is very interesting. I've always thought that since they are all plants, their insides looks the same. I'm obviously wrong. There is a big difference. In aquatic plants I was able to learn that they contain these huge, easily seen air spaces throughout the stem called aerenchyma. Looking at figure 3 above, you can see what I am talking about. These air spaces are very important to aquatic plants because it provides buoyancy and it allows easier circulation of gases. Now after this lab I should be an expert at distinguishing the aquatic plants and terrestrial plants just by looking at their cross sections. Author: John P.
I think Tuesdays are good days for cross sections. Don’t you feel that urge to perform thin slicing of plant tissue on Tuesdays? Seriously, what could be better than identifying monocots and dicots through vascular bundle arrangements!? I can’t think of any other way I’d rather spend my Tuesday. So lucky for me, this week in Oregon State plant structures lab we did exactly that! By looking at the location of the vascular bundles in plant stems, we were able to identify the plant species as monocot or dicot, assuming this wasn’t already known. Taking a close look at the vascular bundles, distinguishing of the individual components of the vascular bundles as well as the surrounding tissue was pretty clear with proper stain types and methods. Corn (Zea mays) is monocot and is in figure 1 and 2 below. TBO stain was used to provide contrast between cell types depending on the compounds present in the cell. Staining with TBO or Toluidine Blue O, will stain pectin substances pink to reddish purple, and lignin, blue or blue green. The vascular bundles are clearly stained blue which is due to the lignin of the secondary cell wall of the tracheid’s and vessel elements, the components of xylem. Phloem is the other transport tissue type found in the vascular bundles, which is composed of sieve tube elements and its dependable loving friend, the companion cells. I remember xylem and phloem and the way materials generally flow through them by saying 'xylem', in a high, squeaky voice, making me think up, and 'phloem', in a low deep voice for down. Say these words out loud a few times and hopefully it sticks in your memory for years to come like it has for myself. The xylem, transports water and minerals from the roots to the shoots and phloem carries sugars, nutrients, lipids, organics, and sad but true, viruses on a bad day. Surrounding the xylem and phloem is a sheath of sclerenchyma which helps with support and also stains thanks to its lignin found it in. Figure 1 and 2 below both help in identifying the regions referenced above.Figure 1 is a corn stem (Zea mays) cross section with TBO staining. In the image you can see the vascular bundles spread throughout the stem with parenchyma cells filling the space between the bundles and the epidermis encasing the both of them. Because the stem cross section was taken near a shoot, the tissue surrounding the epidermis of the stem is young leaf tissue. This image was taken at 40x magnification with a compound microscope. (Prepared by Lucas and photographed by Taylor) Figure 2 is a corn stem (Zea mays) cross section with TBO staining. This image is actually a more zoomed view of the same image above in figure 1. The larger cells in the vascular bundles are vessel elements. You can see two on the outside of the bundle and one or so at the bottom or top depending on orientation. The one or so at the top or bottom with the darker stained outer walls are dead and have possibly been filled with air making them look like bubbles in the slide. Vessel elements are larger transport tubes than the tracheid’s found in the xylem and are prone to air bubbles if breaks in the water tension occurs. This image was taken at 100x magnification with a compound microscope. (Prepared by Lucas and photographed by Taylor) The meristematic regions of the plant are where the new tissue is formed. There are many locations in the plant this is essentially happening. In the figures 1 and 2 above, a region running through the vascular bundles termed, procambium, creates new cells through mitosis. The procambium promotes radial growth of the plant by providing new vascular tissue to replace the non-functioning xylem and phloem. The secondary xylem and phloem get pushed away from the vascular cambium as primary vascular tissue is created giving the stem girth over time. While the pro-cambium provides lateral growth the apical meristem found at the growing tips of plants, (roots and shoots) generates upward and downward growth. Below in figure 3, you can see where the growth is taking place and the name of the region this is occurring. Figure 3 is a prepared slide of longitudinal section of a Coleus shoot meristem. Staining was used, which is apparent in the dividing cells (purple). In the image the leaf primordia, apical meristem, axillary buds, and vascular bundle are all visible. The image was taken at 40x on a compound microscope. (Pre prepared and photographed by Taylor) Figure 4 is an image under a dissecting microscope of a Coleus shoot meristem. In the shoot apical meristem cells are dividing by mitosis and forming new daughter cells that have yet to undergo differentiation. The swelling of these primary cell vacuoles will cause the shoot to move upwards causing primary growth. At some point these cells will differentiate into dermal, vascular, or ground tissue systems. (Prepared by John and photographed by Taylor) - Taylor Bates Introduction This past week in lab was all about learning and exploring the simple and complex tissues of plants. Our objectives were to recognize the three tissue systems of the plant body (ground, vascular, and dermal tissues), compare and contrast parenchyma, collenchyma, and sclerenchyma, identify water-conducting cells of the vascular tissue system and relate their structural features with their functions, and describe the characteristics of the epidermis, which we consider as a complex tissue. My primary focus for this lab was to prepare slides and observe the sclerenchyma fibers of a snake plant (Sansevieria trifasciata) by taking a cross-section and logitudinal-section of a leaf and observe the brachysclereids and tracheary elements of a wax pant (Hoya carnosa). Sclerenchyma Fibers of Snake Plant (Sansevieria trifasciata), Cross Section In order to examine the sclerenchyma fibers, a leaf was taken off of the snake plant. Using a razor blade, several thin cross-sections were taken from the leaf. A cross-section of the leaf was then stained in Toluidine Blue O (TBO) for about two minutes and then removed with a Kim wipe. Ethanol was added to the cross-section and then replaced with 20% CaCl and a cover slip. The reason the cross-section was stained with TBO was to observe the thickened secondary walls, which will be stained blue or blue-green in the presence of lignin. Vascular bundles, photosynthetic parenchyma cells of the mesophyll, and epidermis cells might have been also observed under the microscope (Figure 1). Once the cross-section was observed, a longitudinal-section was cut from the leaf and prepared on a slide stained in TBO. Observing the longitudinal-section of the snake plant leaf we were able to observe the elongated shape of the fibers, located in bundles. We were also able to see lignified water -conducting cells (Figure 2). Tracheary Elements, Sclerids, and Parenchyma Tissue of Wax Plant (Hoya carnosa) In order to examine the tracheary elements, sclerids, and parenchyma tissue in the wax plant, thin cross-sections of the stem were taken. These cross-sections were then stained with CVA. Observing the cross-section of the stem under a microscope, the CVA stained the sclerids and the water-conducting cells (tracheary elements) violet/blue . The outer ground tissue is made up of the parenchyma cells in the cortex and the ground tissue inside the ring of vascular tissue is called the pith. The parnechyma cells and the pith are differentiated into brachysclereids (Figure 3). Author: Austin Wriggle This past week in lab we got up close and personal with some familiar foods to learn about why they look and feel the way they do. The first plant we examined was the red cabbage. We were given cabbage leaves pretreated with digestive enzymes, which we then washed, filtered, and centrifuged. All of this was done in order to remove the cell wall leaving the protoplast behind. By removing the cell walls of the cabbage cells we were able to see them in a whole new light. While normally the cell wall would cause cells to be rigid and rectangular, these cells were circular. The outward pressure that is exerted by vacuoles is easy to see once the counterbalance of the cell wall is removed! Speaking of vacuoles, the vacuoles of the red cabbage are what gives it its distinctive color. As can be seen in the picture many of the smaller vacuoles are filled with blue and purple anthocyanin pigments. These pigments have been shown to have benefits for human health and may even help to prevent cancer. (On a personal note, over the summer I worked on a farm and was able to take home a lot of produce. One evening I made a stir fry with possibly the most potent and powerful purple cabbage in the world and immediately after had the first migraine I've had in years. I don't know that it was the anthocyanins but after that I definitely believe in the power of cabbages.) After we got a good look at the insides of a cell, and watched the cytoplasm move around for a while, we exposed our protoplasts to several different types of solution to see how they would react. Normally a plant cell, unlike an animal cell, has the cell wall to shield them so they can be a bit more resistant to things like changes in the concentration of solutes around them. However, because protoplasts don't have a cell wall, we thought that they would react more along the lines of animal cells. Our predictions were right, and the protoplasts reacted visibly to the different solutions that we tried. Pictured about is how they shriveled up after being treated with salt, but we also exposed them to pure water (some of them exploded) and detergent (membranes were basically melted away, but not very quickly or anything). As well as looking at the insides of cabbages, last week we also covered the insides of other edible plants. Specifically we looked at the ground tissue of pears and avocados. We observed their sclerenchyma cells, which are what gives these fruits their texture. We stained both the pear and the avocado with TBO, which stained the lignified cell walls of the sclerenchyma blue so they were easy to see. When we looked at the pear, it was easy to see that there were a lot of sclerenchyma cells as basically the whole sample was tinted blue. These are the brachysclereids or "stone cells" that you can feel when you eat pears. It was neat to be able to see the pit canals that went through the cell walls, especially when we looked at 400x magnification. It definitely explained why pears have the texture that they do! We also stained avocado with TBO in order to look at its sclerenchyma cells. Like the pear, it had brachysclereids, but it had fewer of them and they were more sprinkled throughout the tissue. In the images above, the brachysclereids are the dark blue dots. Overall the avocado cells seemed a lot softer and blobbier looking, while the pear cells had more clearly defined borders. Avocados are much creamier and softer than pears in general so this makes sense. In fact I would rarely describe an avocado as gritty at all and previously wouldn't have compared it to a pear in any way.
All in all, it was very cool to get to look at some common fruits and veggies under the scope! I really like looking at things that I actually eat because it's knowledge that is directly connected to my life outside of class. Out of everything that we looked at last week, I think I was most interested in the avocado slide because it wasn't what I expected an avocado to look like. I definitely didn't think an avocado would be a great candidate for staining, or that avocado fruits had any particular structure besides just mush. I was happily surprised to be proved wrong! -Ally Kershner Good evening! This week in Botany 313, we got to do some super interesting things. After talking things over with my lab partner and the other group doing a blog this week, I was given the responsibility of posting the epidermises of Tradescantia and a section of coleus (Plectranthus scutellarioides), so this post will focus mainly on those topics. In order to get a slide of the epidermises for Tradescantia, I started off with a leaf from the plant and with a little bending, snapping, and peeling I was able to successfully get a slide with both the upper and lower epidermises present. As shown in the images below, the stomata, guard cells, and pavement cells can clearly be seen on the lower epidermis. On the upper epidermis, only pavement cells can be seen as this type of plant does not have stomata on the upper epidermis. Stomata (plural of stoma) are openings in the outmost epidermal layer in plants that allow for the exchange of gases. They allow for a plant to retain water in times of drought or to increase rate of water loss in times when there is an excess of water. Guard cells allow for the opening or closing of the stomata with the aid of internal signaling (i.e. hormones), as well as external (i.e. The sun or rain). Pavement cells are simple cells with no real function other than protecting the cells below them. The purple pigmentation in these epidermal peels are from naturally occurring pigmentation within the plant. Taking a longitudinal section of coleus and finding the lignified tracheary elements was a bit more challenging. Simply getting sections that were thin enough requires some practice, and finding the tracheary elements, even more so. They are very easy to miss even with the stain! With a little patience, and maybe some help from Dr. L-P, I was able to find a few examples, as shown below. Tracheary elements, such as tracheids, aid in the conduction of water and minerals through the plant. Lower epidermis of Tradescantia with no stains. Wet mount. Epidermal Peel. Arrow shown in image is from compound microscope. Arrow is pointing to stoma flanked by guard cells. The green dots in guard cells are chloroplasts. Cells surrounding guard cells are pavement cells. Photo credit: Michael Billard. Slide Prep credit: Michael Billard. Upper epidermis of Tradescantia leaf with no stains. Wet mount. Epidermal Peel. Arrow shown is from compound microscope pointing to a pavement cell. Purple pigment shown is from naturally occurring pigments within the plant. No stomata can be seen on upper epidermis of plant leaf. Photo Credit: Michael Billard. Slide prep credit: Michael Billard. Lesson Learned: Even with stains and a compound microscope, finding lignified tracheary elements can be very difficult. It can require cycling all the way through (and sometimes back) a focusing cycle, and even then, can be very easy to miss!
Author: Michael Billard Dieffenbachia is one of the easiest indoor houseplants to grow and one of the most common indoor plants. This tropical shrub shows off lush leaves that are usually marked in shades of cream, yellow, or white. It adds fun color and texture into a home. Although it looks like a friendly plant on the exterior, the interior isn't as friendly as you think. Beautiful photo of Dieffenbachia. In order to obtain this slide, we began by grinding up a small piece of Dieffenbachia and added water to it. The picture you see on the left is the wet mount of the beautiful Dieffenbachia . Within Dieffenbachia are cells called Idioblast. They have various functions such as storage of reserves and minerals. Their main function is to protect plants from predators with the crystals that they produce. Idioblast taken at 400x magnification These crystals are called raphides. Raphides are needle-shaped crystals of calcium oxalate that are very toxic. When ingested, it can cause stinging/burning in the mouth, paralysis and airway impairments. Raphides taken at 400x magnification In this video, we can see raphides being ejected from idioblast. How cool is that? Final thoughts!Although Dieffenbachia contains a chemical toxin when ingested, I still think that they are "friendly" plant. They add such warm and beauty into a room that it's hard to consider them a foe.
In this week’s lab, we examined a celery (Apium graveolens)! A celery has many nutritional benefits. It contains antioxidants and beneficial enzymes, in addition to vitamins and minerals such as vitamin K, vitamin C, potassium, folate and vitamin B6. Within the celery stalk contains a left structure called a petiole. A petiole is a small stalk that attaches to the the leaf blade of the plant to the steam. Unstained cross section of celery petiole. (400x) Ground tissues in celery petiole
This is a photo of that vasular bundles, phloem and xylem taken at 100x magnification Lesson of the day! From this lab, I learned that parachyma cells are very easy to locate because they are most abundant in a cell. For some reason, I had a more difficult time locating the vascular bundles. I really enjoyed this lab and can't wait to see what else we get to see!
-Mylinh Nguyen The Technique For Staining: The process of staining potatoes and onions was quite simple – and only took a few laboratory tools. It required:
Once we had our onion epidermis and photo slices we placed the plant material on the slide. Then we placed the dye on the plant material and left it to sit for 2-4 minutes. After, we drew off the excess dye with a kimwipe. Following with ethanol to wash off excess dye, again drawn off with a kimwipe. After, calcium chloride was added and a cover slip was placed on the slide. For the onion we dyed it using CVA. CVA will stain lignin violet and cellulose yellow. In this figure, we can see that onion showed the violet pigment in the cell walls of the onion – which was inspected. Also notice the beautiful vacuoles that are clear in the cell! Stained Onion Cells at 400x Magnification Photo by Melissa Clark and Cierra Walker The potato was stained with iodine – iodine would highlight starch within the potato cells. We were lucky enough to look at a greening part of a potato! This meant that some of the potato’s cells has begun the process of switching amyloplasts to chloroplasts. Amyloplasts are specialized plastids for starch storage. It’s easily observed in the shot above that as the amyloplasts change to chloroplasts – they lose their capacity to store starch! Notice how the dark black spots fade to green-stuffed cells! Stained Potato Cells at 100x Magnification Photo by Melissa Clark and Cierra Walker Staining Plant materials was not and is not a difficult task - and in doing so, you can make certain cellular components more visible!
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