Hello and welcome to HORT 201. This is module 3.1 Horticultural Science and Practice and this is Lorenzo Rossi. So, we are at module three. We are at week three and we are going to talk about how to identify stages of plant growth from seed to fruit. So, we're going to go around the entire life cycle of a plant. And at the end, you should be able to identify the different stages, plant growth, primary and secondary growth and explain the differences, but also we will talk a little bit about the cambium and its role in plant development. So, I put this example here to give you an idea, because we're going to start from the seed. We're going to talk a little bit about the seed. We're going to talk about seedlings and we're going to talk about young plant, mature plant, and then flower, fruit and this going to be all module three. So I'm going to talk a little bit about this in 3.1 and more in the other one. Let's start with the seed. I put this example here. Those are two different seeds. One monocot, one dicot. But there are four, actually three things that I want you to remember. Each seed has a seed coat. That's a protective layer outside the seed. And then inside that seed coat, there is an endosperm. Now, that's your storage that is packed with all the things that seed will need to germinate to emit that first root and first leaf before the roots can start taking up water and nutrient from the soil. We have the endosperm that give them protein and a little bit of fat. And that's why when we eat nuts, when we eat particular seed, if you eat an almond, if you eat a pecan, you are eating the endosperm. And then there is an embryo. That's the actual plant. That's what going to develop into a plant. That's the produce of the union of the pollen and the, and the ovule. So the male and the female part together, they create the embryo and they create that seed. Now monocot, dicot, I don't really care, there are different parts but the endosperm, the seedcoat, and the embryo, those are the one that I want you to remember. And I put here some examples. So this is rice. So example of seeds with a coat and several seeds on on the same is an inflorescent that then became a seed. See this is the seed, these are the coats of that seed. That white stuff, that's your endosperm. Wheat, we have durum wheat, bread wheat. A lot of people always ask me a questions, what's the difference between the pasta and the flour but the pasta and the bread that we. The pasta is a Triticum durum, so that's your semolina and that's different from flour. Flour is Triticum aestivum, so there are two different varieties of wheat. They have two different type of seeds, even in terms of size and shape, they're both wheat, but one is good for pasta, the other one is good for bread. Beans, another example of seeds. We eat them. We eat those seeds and they are in pods. See, this is a legume, multiple seeds in one pods. And then we have pecans. Pecans are nuts that are in a shell. They're protected, and then will go to the shelling plan. We remove the shell, and we make them available to make your pecan pie or just to eat them as they are. These are all example of seeds. And so what happened? We go from the seeds to the plants. What is the trigger here? Water, oxygen and temperature. This is what you need for your small seed to germinate. See, you go from the seed then the radical, then from the radical it goes into a new plant, and this is a dicot so we're going to have two leaves. And here I put more information so in these slides, you can see from seed to seedlings the various components, so the the the small radical, the water, the shoots, and then there's several thing that happen during the germination process and then the role of the sunlight at the end. So we talk about the seeds and now we have a seedling right? Now what? Well we need to talk about meristem. So we are going to introduce a new term which is the apical meristem. This is, we talked about tissues right? This is another tissue and in order to have a growth, we need to have this apical meristem on the tip of the shoot and the tip of the roots. They will be responsible for cell division elongation and so basically the plant will grow in two different direction looking for sunlight, looking for water at their roots. So as I say, we talk about vascular tissue, parenchyma tissues, sclerenchyma, collenchyma. Now we're going to talk about meristematic tissue. These are made up of cells and they continuously divide. This is the property of meristematic tissues. They keep dividing and they are responsible for the growth and the development of the plant. You have a apical meristem on the top. You have a apical meristem on the tip of your roots and they will keep growing and that's why the roots will keep going deeper and the plant will keep growing, will keep growing taller. Do they always just go up and up and down and down? No, that's a primary growth. There is also a secondary growth and I put some example here. So the primary grow is a elongation. The secondary grow is thickness. So increase in girth or the diameter. So primary growth make the plants taller. Secondary growth makes the plant wider. If you get this concept, now we're going to go a little bit more into detail. And remember, not all plants have a secondary growth. Most of the woody trees do but the grasses don't. They will just get tall, they will die and they will regrow. How this is all happening? All the growths are responsible are made possible by the cambium. So this is a meristematic tissues that goes to increase the stem and the roots in terms of girth. And we have a vascular cambium and the core cambium. I don't want to get into much details here but if you think about the annual tree rings, and then we will get there in a minute, you would see that the idea is that you have a meristematic tissue that goes elongation and you have a cambium that goes into diameter and again mostly in tree crops. So, how does the primary growth happen in roots? Well, we have a root cap, right? And you remember we talked a little bit about this. The root cap is a protective cap. Think about this. Roots, the major role is to go deeper, search for water and nutrients and absorb them, right? But they have a lot of obstacle while they're doing that. So having a protective structure like a root cap help them and protect the meristem. They also secrete mucilage and that is that penetration that the roots are going through into the soil. Right above the root cap, there is the meristematic zone. That's where you have the elongation zone right keep growing growing growing growing growing. And then we go into the differentiation zone. That's when the cell mature and that's when the cambium we were talking about starts having a role. The other thing we can talk about, lateral roots. From one roots you can have these lateral roots coming out and you may think they're coming out of the epidermis. The answer is no. They come out from the pericycle. Why? Because we need those lateral roots to be connected with the vascular system. So they come out from the pericycles. There is an example, from one roots you get all these lateral roots. The primary growth that we talk about in the roots is pretty much the same in the stem. You have the apical meristem and it goes into the primary tissues and it keep elongating, it generate the epidermis, a little bit of cortex, primary xylem, and the pith, and again this is a elongation. When we have both the primary roots and and stem we also have a secondary growth as I say and this is mostly in woody species. And in these cases, again, it's the growth in girth or diameter and I put some examples here, but the major thing is that the cork, cambium, the phellogen, will push for the bark, and the vascular cambium will create tissue inside, and so with these two continue growing you have one more ring, because every year you have this deposition of new tissue. And so, with the apical meristem growing making the plants grow up and down, so taller and deeper, and the secondary growth making that grow in diameter. That's your growth and development. And that's how from a small seedling in 10 years you get a nice looking tree. And now we have reached the point in which we have pretty much a crop and we start having buds, right, and we start talking about original, new plant structure. Bud differentiation is one of the most important topic if you want to have a production because the bud differentiation is when we're going to talk about having a bud that is going to go into leaves or it's going to go into flowers. And if it doesn't go into flower but it goes into leaves, it means you're not going to have a production. And that's where it gets tricky, because there is temperature, there is pruning there is raining, there is fertilization, there is a lot of factors that affect this bud differentiation. And I say we have vegetated buds, they could just become flowers, they have reproductive buds, and we have mixed buds. Now the question is how do I pick or how do I make one bud to be one or another? The answer is not easy. There is a lot of environmental factors and the meristem cells will start dividing and that's where we, and then after that we have a commitment. So you either go vegetative or go reproductive. If you go vegetative, that bud is going to become leaves. If we go reproductive, that buds going to become a flower. And that's where it's tricky, because sometime they there is a need of temperature, cold, in order to get the flower induction, or maybe water, or maybe nutrition and then after that we have the development and the maturation. So what are these factors? As I say, photoperiod, and we will talk about this, there is specific chapter, temperature, we have a specific chapter about that, water availability, hormones, and pruning. All these are going to get discussed in this course by the end of the semester. But all of these together are what are going to influence your bud and in the differentiation. Some plants, most of the temperate one like apples, some of the peaches, they are chill, they need require chill. If they don't get enough chill they don't flower. That's why sometime it's hard to grow olives in Texas because we don't get enough cold or we get too cold during the winter. Some others like citrus, they don't really need cold because they're subtropical. They need water availability and that's their trigger. When we go into the wet season or the dry season, that' where they change their physiology and that's what differentiates some temperate trees from other type of trees. But they usually, they need a trigger to get into that reproductive phase. I think that's enough for this module. We're going to talk more about this in the next one. But remember, we started with seeds, germination, growth, primary and secondary, and then bud differentiation. We talk a little bit about primary and secondary growth, vascular cambium, core cambium, and also we talk about these buds and how they specialize into vegetative or reproductive. Module 3.2 two is next and this is going to just continue on this topic. Thank you.