CSUN BIO107L Stomata Exercise

hello to everyone welcome to your virtual learning experience this is the final part of this week’s lab which requires you to perform a dissection of a plant leaf to observe stomata on the upper and bottom side of the leaf before we get into the procedure I would like to give you some background on stomata specifically some functions where they are found and then eventually at the end we’ll see what they actually look like so stomata are openings found on the epidermic layer of plant leaves stomata have various functions but there are two that are crucial for plant’s survival the first is the ability for stoma to open and close when stoma open they allow excess water to transpire out of the plant or in times of stress and drought the stoma remain closed to retain their water supply besides water control stoma also regulate gas exchange when carbon dioxide is required for photosynthesis the stoma will open and allow the plant to breathe in atmospheric carbon dioxide so that it can metabolize and create sugars so where do we find these stoma some are located on the underside of leaves they are found on the bottom sides of leaves because it is generally a more suitable environment on the underside it is shady so there’s less heat as well as lower humidity the underside is protected from UV radiation as well as heavy rain due to a waxy cuticle found on the upper layer of the leaf the suitable environment allows sensitive organelles such as stoma to function properly in gas and water exchange so now that we’ve taken a look at the functions of stoma and what where they actually found let’s go ahead and get into the procedure the goal of this exercise is to dissect a plant leaf and remove its epidermal layer from both the top and underside to determine where stoma are located the first step is to remove one leaf and very gently push some tweezers into them between the epidermal layer and the mesophilic layer the mesophilic layer is going to be that green spongy good stuff it’s gonna have chloroplasts enriched molecules so we want to actually avoid that we’re more interested into the skin of the plant which is the epidermis so we’re gonna use tweezers to carefully peel away a little cross- section of epidermal layer from the leaf and then we’re gonna go ahead and put it under a microscope and see what it looks like so what you’re seeing here is the top side of the plant leaf the left side is a 4x magnification and that is where you should always start it’s always important to start at your lowest magnification and then increase in increments so that you do not damage any slides so we’re gonna start in 4x and as you can see there isn’t quite much to see there are no distinct features there are no unique structures so something gives up here so we’re gonna take a 10x magnification and take a look at it closer up so what you’re seeing still is pretty much nothing the top layer does not contain any significant structure or organelles included in metabolism or other important aspects of a plant’s life it is simply there for structure and support integrity so at the 10x again we do see nothing so let’s go ahead and take a look at the bottom side so this is the underside of the leaf and this is a 4x magnification as you guys can see there is a little bit of green stuff to go with it this is on just a byproduct of trying to remove an epidermal layer from the bottom side it does not come off easy so as you can see there are quite significant differences we do see some porous black looking things but that’s not the whole story so we need to get a little bit closer so we’re going to move to our 10x magnification and you can now see where the pointer is I am pointing directly at a stoma it looks like a bunch of eyes or a bunch of open mouths whenever you see this just default to stoma that’s what we’re talking about here so although we have a better picture of what’s going on here and what’s found at the surface it’s important to understand what these things actually do and to get an idea of what they do we need to look the closer so I went ahead and went to 40x for this slide and now we have one individual stoma in high definition very close-up and what we are seeing here is the mouth so where my my mouse pointer is that is the actual mouth of the stoma and what’s surrounding that mouth are these yellow greenish like cells these are called guard cells the guard cells are involved in regulating the opening and closing of stoma so in the presence of too much carbon dioxide or too little carbon dioxide or too much water or too little water they will induce some mechanism which opens and closes the stoma with this information I’m going to go ahead and cut it off here so if you please feel free to take the survey at the end of the video which you will be responsible for in your future classes and if you have any other questions feel free to ask your instructors thank you .