 Good morning class, today we're going to be discussing plant structure and plant growth and we've got an outline on the board in terms of the topics that we're going to be covering today. First of all, in terms of plant structure, we're going to look at the hierarchy of the organization of plant structure and we're going to look specifically at the organs, the tissues and the cells associated with plant structure which perform specialized functions for the plants. Plants are very amazing creatures, very exciting, you know a lot of us may not pay attention to plants but without them we cannot survive and so in terms of the organization, plants from the aerial parts are utilizing the light and carbon dioxide as nutrients that they need for photosynthesis and in terms of the underground parts, the root system, they utilize in water and minerals from the soil. So as we look at the organization, keep in mind the functionality of these structural components of the plant in terms of the most important process in my opinion, photosynthesis which is providing us with the food that we all are dependent on, the energy that we need. Okay, we're also going to look at the function in terms of our structure and growth so the structures organized so that the plant can grow in a particular manner and we're going to talk about the type of cells and plants that are really responsible for plant growth. These are called meristems or meristematic tissue. It sounds like a shoot system, it sounds like the stem but it's actually an area of actually dividing cells. We'll talk about the different types of meristems today and basically how they contribute to the growth of the shoot system and the root system and then plant grows in two ways. They grow vertically, they grow taller, that is referred to as primary growth and then they also grow wider. The stem gets thicker, increasing good, increasing width and that's secondary growth. I will discuss that today as well. So let's get started. In terms of the organization, the three organs associated with plants or the three organization of the plants or the organ system and then the tissues and the cells but we need to define organ in case you forgot. An organ or a group of tissues formed together that serves a specialized function and in the plants the three organ types are the roots, the stems and the leaves. That's the organs within the plant, root stems and leaves. Now as we look at the root stems and leaves, we're going to talk about specifically the flowing plants today which are known as angiosperms and rarely you have two categories of angiosperms. We got monocuts versus eudicuts. So as we talk about the organization, the structural organization of the root stems and leaves, we'll also look at a different in the organization of the monocut flowing plants versus the dicuts in terms of these organs, root stems and leaves. Okay. When we look at the tissues, there are three major plant tissue types. We've got dermal which is the covering tissue. Dermal tissue is the covering tissue. It's kind of like the skin of the plant is analogous to the skin. Nobody's the skin covers the body. So the dermal tissue is the covering tissue of the plant and on the leaf, there's some specialization on the stem. There's some specialization in terms of the dermal tissue, specifically to prevent water loss, dehydration. That's one of the major obstacles that plants face on land desiccation. So there's some specialization in the dermal tissue to account for that. We've got vascular tissue which is a transportation tissue, the transportation vessels within the plant. This is what enabled plants to transition from water and existence in water where they're dependent on water for transport onto land, terrestrial plants which develop their own vascular tissue enabling them to transport nutrients throughout the plant. And then we've got the ground tissue which is the packing, the supporting tissue that's just there to help support the structure of the plant and for storage and so forth when the plant makes its food. The ground tissues areas where you have a lot of the storage taking place, a lot of the support and a lot of the metabolic activities that are going on within the plant takes place in the areas of the ground tissue type. Now as we look at the cells in plants, there are really five categories of plant cells that covers all the tissue type okay. So we're looking at organs being the largest structure within the organs we've got tissues and within the tissues we've got cells the cellular level and so these are the different types of cells that we can find in a plant. First of all we have some unspecialized cells that are most abundant throughout the plant in the ground tissue known as parenchyma cells. Parenchyma cells, primary cell walls very undifferentiated a lot of metabolic activities takes place in the parenchyma cells of the plant. Then we have colenchyma cells. Colenchyma are slightly thicker cell walls than the parenchyma cells they predominantly allows the plant to have more stability, more support but still flexibility for growth and then we have the most differentiated of the three sclarenchyma secondary cell walls and there's a material called lignin that lignifies the cell walls makes it very rigid very tough structurally tough and those are the sclarenchyma cells found in the plants and you know in terms of secondary growth you would find a lot of sclarenchyma cells because the plants and has to support the height and the weight of the massive plants as they grow. Okay then we have a type of cells known as xylem vessels containing two types of cells. Xylem vessels are made up of trachids and vessel elements so there are two types of cells found in the xylem vessels and the xylem vessels are responsible for transporting water and minerals in the plant so we basically talking about absorbing the water and minerals out of the soil out into the root system it gets directed into the xylem vessels and then it gets transported up the plant predominantly to the leaf area where photosynthesis is going to take place so these vessels the xylem vessels have two types of conducting cells that are responsible for transporting again water and minerals then we've got the fluem cells. Fluem is made up of sieve tube elements these are conducting vessels of the fluem vessels and companion cells which are neighboring cells that basically nourishes the sieve tube elements keep them alive and keep them healthy over time supporting but the conducting vessels of the sieve tube elements the fluem is responsible for transporting sugar and other organic nutrients that the plant makes in the leaves area of photosynthesis and transports it to other areas of the plant where it's stored predominantly in the roots but plants have modifications sometimes and you may have some organs of the stem that store food made in the leaves transported by the fluem vessels okay so organizationally plants are organized into their recapping their organs their tissues and their cells structure being related to functions these organs are nicely specialized for the function that they serve the root system and the shoot system adapted for the lifestyle of the plant remember plants cannot take themselves up and change location once rooted that's where they're going to live that's where they're going to reside and they have to survive in that environment they're very very adaptable and the organ system and shoot system rarely speaks to that adaptation in terms of the organization which we just talked about