PlantOrganismEmulsionDamageScratches

the world of green plants that surrounds us on every side at first you might think that they didn't really have very much in common because they seem to differ so much in size and in shape and in the kinds of parts that they're composed of but actually all of the larger green plants have a great deal in common in their structures and in their functions as is the case with animals the green plants May consist of organisms of only one cell or organisms of many cells and the larger green plants are multicellular organisms and we're going to concentrate our attention primarily on the multicellular green plants that produce seeds although we will mention some other types as well now as you examine the parts of a multicellular plant you find that under a microscope we can see that each of these parts or structures is composed of many cells as is shown in this model now the cells of the plant do different things some of them carry on photosynthesis some of them are protective some of them conduct food materials and other substances from one part part of the plant to another and still others absorb substances from the environment now each of these kinds of cells is different in shape and structure in general from the other kinds a group of cells that are all of the same general sort in their shape and size and all do the same thing in the activities of the plant are called a tissue and some plant tissues carry on photosynthesis some are protective and cover surfaces and so on as you examine this model of the root you can see that there are masses and patterns of different types of cells which are the tissues of the root now groups of tissues that work together and form larger structures with Cooperative functions groups of tissues of this sort form the organs of the plant such as the roots and stems and leaves we can go one step further in our pattern of organization and say that related organs may form a in the plant body now ordinarily the organs appear when a seed begins to germinate and by germination we mean that the cells the tissues in the seed resume an active growth they were alive all the time but they hadn't been actively growing and developing until the seed germinate and this applies to other structures such as spores as well when the seed germinates first the underground parts of the plant body appear the root and Branch roots which would form the root system of the plant next appear the parts that ordinarily grow above the ground the Chute system which produces the stem and the leaves and branches eventually flowers appear and flowers are reproductive organs and finally the fruit and seeds which brings us full cycle in the pattern of development of a multicellular seed plant now ordinarily you think of plants these multicellular ones as stationary they don't move around very much and this is true in only a few cases are there active moving stages in the Life histories of plants however a plant isn't static even though it's in one location most of the time all through its life it is continually developing it grows and changes as long as it's alive now the process of development can be divided into two general Parts one of these is growth and growth is fairly easy to see and to understand because it is increase it's increase in the number of Parts such as the cells or in the size of those cells or sometimes in the amounts of materials that the cells produce but growth is increase and fairly easy to observe the other part of the developmental process is that of differentiation and this is a little bit more difficult to explain by differentiation we're referring to the process which occurs when the relatively simple small cells that are produced in the growing parts of the plant in the stem tips and root tips for instance the ways in which a cell of this sort may become changed and modified in shape and structure and function into cells of the leaf or other cells of the same kind may become uh very heavy walled and Stony and the cell itself may die as in the hard walled structures of a peach pit or a cherry pit or some of the same kind of cells may become conducting cells in the stems and veins of the plant now by differentiation we mean the things that happen in producing all these different kinds of cells doing different things and having different structures in the plant now both growth and differentiation require not only the proper nutrient raw materials from the environment but they require a great deal of energy and the energy used comes from the processes of photosynthesis and respiration let's review the general pattern of what we know about these two aspects of the metabolism of the cell in photosynthesis the requirements are light energy from the outside source and chemical energy released from the activities and Machinery of the cell the raw materials of water and carbon dioxide then these raw materials along with minerals and other nutrients in the cell organization which includes the chlorophylls all of these things produce the carbohydrates first containing the stored chemical energy that came from the sunlight then other organic compounds are produced later water is proded produced and oxygen is produced as a byproduct or as byproducts and the chemical energy that is trapped in those carbohydrates from sunlight respiration on the other hand requires not only the chemical energy that is released in the cell's activities in high energy phosphate bonds but it requires the carbohydrates with their stored supplies of energy and water and oxygen in aerobic respiration then in the cell organization the chemical energy of those carbohydrates is released in a form the cell uses in its activities and the waste products of water and carbon dioxide are released so in photosynthesis and respiration we have a transfer from light energy to the energy of organic compounds such as the carb carbohydrates then the release of that energy and respiration in forms that the cell uses and it is this kind of energy that's used in growth and in differentiation now we could expect then that the different parts of the plant the organs of the plant are related to these processes of photosynthesis and respiration in some very special ways the main organs of the plant as the roots and stems and leaves cooperate in achieving the transport and bringing together of the materials necessary for photosynthesis and distributing the results and products of them around the plant the root anchors the plant it extends through the soil and all directions from the point of its original growth and while root systems vary a great deal they Supply support and Anchorage to the above ground plant parts another thing that the root does is absorb minerals and water which are necessary for the metabolism of the plant and for photosynthesis and for further organic synthesis they also frequently store food materials sometimes in quite large amounts you're all familiar with a number of our common vegetables which are examples of very great storage functions in The Roots turnips beets uh radishes carrots all of these of course have by plant breeding and selection been made much more um effective storage organs but they were storage in the plants in their wild State and it isn't just uh roots of this sort that store sugars and food materials even in the case of ordinary root some degree of food storage occurs and the evidence for this can be seen in the sprouting that occurs in new shoots where the only food supply before photosynthesis occurs must come from root storage the stems of plants are the parts which support the leaves the stems and branches they also are the main vertical transport portion of the plant materials moving both up and down in conducting parts of the stem here is an example of a very important stem that of sugar can and in the juice of this a large amount of carbohydrate is stored and one that's a very important material to us of course the stems must be ground and the sugar extracted some stems even have chlorophyll the outer layers of cells carry on photosynthesis and can share the function of food manufacturer with the leaves the main function of a leaf is that of photosynthesis carbon dioxide from the air entering the leaf transportation system of the plant brought in from the roots and stem chlorophyll present in the leaf and sunlight striking it in the cell Machinery carbohydrates are synthesized the carbohydrates and other organic materials leave the leaf and are distributed to other parts of the plant now after having listed these main characteristics and functions of roots stems and leaves uh of course in nature adaptation and variation in function is one of the outstanding characteristics of living things Roots we ordinarily think of as being underground well sometimes stems are underground too the ordinary potato is a specialized underground storage organ derived from stems and the eyes of the potato represent the leaf scars or Leaf buds that occur normally on stems this type of modified structure food storage in an unusual location is called a tuber there are other kinds of strange modifications Roots aren't always underground either in some of the orchids and a number of other plants there are aerial Roots completely above ground and some of them even have chlorophyll and are green and perform a certain amount of photosynthesis another example in very commonly in ferns is that of an underground stem which is called a risone the structures you see above ground in most ferns are not stem and leaves but all parts of a sing single leaf if the plant is removed then the stem can be seen or ryome as an underground stem with the roots attached to it all of this below ground leaves Also may have strange and different modifications in one group of plants they have become specialized for the trapping of insects the exact function and role of this or the reason for its uh evolution is not quite clear most insect trapping plants live in soils with low nitrogen and of course animals would have protein and considerable nitrogen and it's possible that there is a relationship between the leaf insect trapping adaptation and nitrogen in the soil there are cases where leaves are highly modified too in the cacti many strange modifications occur most of what we think of as the plant and its leaves are modified stems in many of them the spines are changed and modified leaves now the life history or life cycle of a plant can be divided into two main phases the vegetating phase which is concerned with the production and storage of food and with growth and the development of the individual the growth and differentiation of the individual plant and the reproductive phase which is concerned with the production of new individuals with the new generation now there are some plants that have specialized structures that result from growth such as runners or stolen that produce new plants vegetatively through growth and as these runners or stolen radiate from the parent plant new individual plants appear and grow and if they become detached we could say that reproduction of the individual had occurred this is called vegetative reproduction but the main reproductive organs of plants are flowers and cones and spor cases flowers and Cones produce seeds and the seed is a very specialized kind of package that contains membranes and stored food material and a small embryo plant that is in a resting or inactive state of growth inside the sea spores on the other hand are produced in Spore cases by Ferns and by mosses very commonly and in this example of the ferns we can see Spore cases on the underside of some of these leaves as dark areas and with a knife I can remove some of these spores which when fully mature are easily uh scattered now seeds and spores differ in several ways the small embryo plant in a seed has been the result of the fertilization of an egg of sexual reproduction whereas the Spore contains usually a single cell and is the result of just ordinary cell division and some specialization it is uh asexual reproduction but both seeds and spores are means by which the stationary plant is able to get into new locations and to increase its range these are means of dispersal seeds and spores can be carried by wind they're often carried by water and very frequent by animals birds that eat the fruit and ingest the seeds or uh seeds that stick to the fur of animals and so even though the adult plant is stationary after the seed is germinated and we can regard the seed you see as the end of one cycle and the beginning of another one the seed or Spore is a means of spreading the plant from one location to another now we can summarize these interrelated vegetative organs of the plant those concerned with development of the individual the roots and stems of and leaves as continuously developing through growth and differentiation The Roots spread through the soil from the point of origin coming in contact with more water and with more minerals as they grow the Chute extends upward producing new leaves and new branches carrying on photosynthesis and supplying the food materials and energy which is necessary for the whole organism the energy expended in growth is more than made up by the accumulated energy of photosynthesis and this is our cue to one of the main inter relationships among living organisms the dependence of plants and animals on these particular cells the cells with chlorophyll although there are some other forms of self-nourishment cells trapping the energy of sunlight manufacture the basic organic compounds which Supply foods and Structural Materials for most other organisms if we think of this Frame as representing an entire green plant then we can see that only some of the cells even in the multicellular green plant contain chlorophyll and perform photosynthesis most of the cells in the roots and a lot of cells in the stem tissues are without chlorophyll and these are dependent for their organic foods on the chlorophyll containing cells in turn however there is an Mutual or interchange in that these cells Supply the photosynthetic ones with water and mineral nutrients this pattern of dependence on chlorophyll extends through the whole Living World there are plants that have no chlorophyll at all some of them include seed plants that are colorless or some as in the fungi uh that may be either colorless or perhaps have other pigments uh that are not chlorophyll but these food these organisms must get all of their organic foods from the green plant either the cells without or with chlorophyll this is the basic source and of course all animal organisms either feed on green plants directly or they may feed on non- green organisms that have gotten their food materials back here or in some cases they feed on animals that have fed on animals that have fed on Plants but in a sense the greenness of the living world that surrounds us is a mark of its dependence and interdependence on the process of photosynthesis organisms as we know them today animals and plants and even the non-living world the physical environment would not be the same if it weren't for this tremendously important energy trapping system of the green plant [Music] oh [Music] I [Music]