 Now, as we look at the growth aspect of plants as it ties back to the structure, different meristems generate cells for primary and secondary growth. So we're going to talk about these cells called meristem. Remember, these are not, this is not a chute system, these are specialized cells involving cell division. They're called meristems or meristematic tissue. Now we've got two types. We've got the apical meristem, responsible for primary growth. Apical meristems are formed on the chute tip and the root tip. Now if you were to remove the apical meristem, a process called pruning, if you enter gardening, folks prune their hedges and so forth many times, and the goal of that is to prevent the primary growth, the plant getting taller, and to sprout lateral branching. So if you were to remove the apical meristem, the apical meristem is responsible for phenomenon in plants known as apical dominance. So what is apical dominance? Once the apical meristems are active, the plants are always going to grow taller, and the axillary buds which are responsible for lateral branching are going to be inhibited. So once the apical meristem are active, the axillary buds are suppressed. Now if you were to remove that apical meristem, then you've removed the apical dominance, and then the plants, the axillary buds can sprout and generate lateral branching, and the plant starts growing wider than it does taller. Now why is the plant always growing taller than it does wider naturally? Because it has to get that vertical height to receive and trap sunlight, the most important energy source that helps the plant in the process of photosynthesis. Remember it's capturing sunlight, it's taking in CO2 in the leaves, it's taking in water, and minerals from the soil, mixing it all together in this very special process again called photosynthesis. There are different types of apical meristem responsible for the different types of tissues that the plants generate. So the three types of apical meristem that you need to note is you have procambium, which gives rise to vascular tissue, you have protoderm, which gives rise to ground tissue, sorry, you have protoderm, which gives rise to dermal tissue, okay, remember the three tissue types again, dermal, vascular, and ground. So procambium is an apical meristem that gives rise to vascular tissue, protoderm is an apical meristem that gives rise to dermal tissue, and the third type is ground meristem, which you can probably figure out by now, gives rise to the third type of tissue, ground tissue, okay. So this is primary growth, and the three primary or apical meristems responsible for the tissue type, which then develops into the organs which we've spoken about already. And then in terms of secondary growth, we've got lateral meristems responsible for that secondary growth, and they are two types. We have vascular cambium and cork cambium, okay. So once you hear the word cambium, think meristematic tissue of course, procambium, vascular tissue, and then in terms of the lateral meristem, vascular cambium and cork cambium. The vascular cambium gives rise to secondary xylem and secondary phloem. So once again, once you hear xylem and phloem, you're thinking water and minerals and xylem, sugar and other organic nutrients and phloem. So this is secondary xylem, secondary phloem, developed from the lateral meristem, the vascular cambium. The cork cambium gives rise to cork, okay, which is again ground tissue type that supports the plant when it's undergoing secondary growth, okay. So the cork cambium and the cork together makes an outer layer. If you ever look at a tree, okay, it has this rough texture on the outside of it, known as periderm. And the periderm is just that protection, again, from the tree, from drying out harsh conditions and it also creates some rigidity to the tree and support because, again, it's going to grow tall, the weight is going to get heavier and you don't want it to break on its own weight. So the cork cambium supports in that regard so that we have these trees, some of them as tall as 110 meters in height and very wide in diameter. So this is lateral meristems giving rise to secondary growth, primary growth, secondary growth. Now as we talk about organization again, I mentioned monocots versus dicots. I'd like to kind of bring this to a close by looking at the organization on a cellular level because in lab you're going to take a microscopic view of the monocot root stems and leaves versus the dicot root stems and leaves and that organization that really surrounds the vascular tissue associated with monocots versus dicots. So let's take a look and for this I'm going to draw out the shapes as I discuss them so that you can get a better perspective of what they look like, you're going to examine them in the lab and that should make sense to you when you see them again under the microscope. But as we compare the monocot versus dicot root stems and leaves and we look at the organization specifically we're going to look at the arrangement of the vascular tissue namely the xylem and then the fluem vessels in between the xylem vessels. So if we put up a little chart we've got monocot versus dicot and then we've got root, stem and leaf. As we look at the monocot root you're going to see that the arrangement of the vascular tissue forms a ring arrangement, has a characteristic ring arrangement so a very circular pattern of the xylem vessels in this ring formation. When you look at the dicot root you have sort of a star like appearance of the monocot or the dicot sorry the xylem vessels. So we call this a ring arrangement, we call this the star arrangement or the cross. There's a characteristic difference in the monocot versus the dicot. Now keep in mind monocots do not undergo secondary growth. They are the herbaceous plants on the planet, dicots do. So with that in mind structurally they arrange differently in terms of their vascular tissue and the transportation of these nutrients within the plant. As we look at the arrangement of the stem for the monocot stem you have a scattered arrangement. The vascular tissue is scattered so a ring arrangement in the root a star for the dicot for the monocot scattered arrangement. So again there's no set pattern scattered means there's no organized pattern, it's just everywhere throughout the stem whereas in the dicot you actually have an organized ring similar to the monocot root but the ring is further to the outside of the stem in a dicot. This is very important because again when you look under the microscope the only way you can differentiate guys is through the organization is through these vascular arrangements and you're going to have to become very familiar with these in order to differentiate monocot dicot. The leaf if you think of the external leaf of a monocot versus dicot which taxonomists use as a criteria the leaf arrangement the venation in the monocot is parallel okay they're parallel to each other so if you were to leave class and grab a leaf and take a look you may see these parallel veins you can tell that's a monocot plant that you're looking at. The dicot leaf externally has a net like pattern okay a net like venation or articulate as opposed to parallel so now if you were to take a cross section and look at them under the microscope the vascular bundles of the monocot will be all basically the same size because of the parallel venation but in the dicot because of this main vein and then the secondary veins running off of the main vein you would have a very large centralized vascular bundle and then smaller vascular bundles centralized vascular bundle which represent this main vein that's the dicot pattern. So guys again as we look at structure plant structure and plant function they correlate always the organization has a lot of terminology that you need to know the key terms being the types of cells the types of tissue the organization in terms of root stems and leaves and then how is that associated in the most abundant plant group the angiosperms looking at a dicot versus monocot and pulling that together in terms of plant function. When we continue on next series we're going to look at growth again in terms of primary and more detail secondary and the structures associated with that and then how that influences the physiology of the plants as they grow and adapt to different environments thank you.