Blog by Max McDonald Week 5 already in the books!! Wow the term really does fly by when your having so much fun learning about plant structure and botany with Dr. LP! Any way get ready to learn about some leaves and grass for your cat. First things first, whats up with these leaves? Just bud + leaf? simple right? Wrong! In the above image we see an example of a compound leaf. Compound leaves form from the same place as simple leaves, axillary buds. Compound leaves are made up of a petiole, that stems from the shoot, and multiple leaflets growing directly from the petiole. It is easy to mistake leaflets for leaves, but don't be deceived by their similar form and function! Leaflets come in clusters, on petioles, while leaves come directly from the shoot, one petiole to one leaf. I took the above image in class last Thursday. You can clearly see all of the the features that make up a compound leaf. A petiole stemming from an axillary bud, 5 leaflets stemming from the petiole, the bud sitting above the petiole, and even some axillary prickles! ouch! I could talk about compound leaves all day! so cool ! but, there are more pressing leaves at hand now that you are informed about the complex ones. Buckle up. I bet your wondering about the arrangement of leaves on a stem or axis. me too. If only there was a word for that...Well, I hope you buckled up, because guess what? There is. Phyllotaxy comes in many different forms, but in the interest of brevity, i'll only enlighten you with two. Firstly there is opposite phyllotaxy. In opposite phyllotaxy the axillary buds stem from opposite sides of the stem, just like in the below picture. Secondly there is alternate phyllotaxy. Unlike opposite phyllotaxy the axillary buds in alternate phyllotaxy's alternate down the stem. This leaves open space directly across from and bud on the shoot. The image below is an example of some alternate phyllotaxy on a piece of english ivy from lab. When is this guy going to get to the catgrass?! Don't worry, right MEOW! Below is an example of a cross section of the aforementioned grass for your cat, more commonly known as wheat grass, a C3 grass. You can see the upper epidermis, which uses translucent cells to focus light into the mesophyll cells. Also visible in the middle of the cross section is a vascular bundle. At the very bottom of the cross-section is a stoma. The stoma is a pore in the grass that allows for greater absorption of CO2. The stomatal pore is opened and closed by guard cells on each side. The CO2 enters the stomatal pore and absorbed by the water that surround the mesophyll cells. Check out the stoma and guard cells visible is this epidermal peel below! interesting and beautiful!
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AuthorContent is created by students participating in the Plant Structure course at Oregon State University for Winter 2017. Archives
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