EXPERIMENT 9: Plant Tissues
OBJECTIVE
To identify the function of plant tissues and types of roots, stems and leaves. To describe the characteristic and function of plant tissues.
MATERIALS
1) Razor blade. 2) Clean microscope slide. 3) Coverslip. 4) Prepared slide slide of buttercup buttercup (Ranunculus) (Ranunculus) root, c.s. 5) Prepared slide of corn corn (Zea) root, root, c.s. 6) Compound microscope. 7) Distilled water in dropping dropping bottles. bottles. 8) Germinating radish seeds in large petri petri dishes. 9) Demonstration Demonstration slide of Casparian Casparian strip in endodermal endodermal cell walls. walls.
PROCEDURE
1) Compound microscope microscope was adjusted, the specific area was located, the field of view was centered and slides that contain section of sambucus bark, Helianthus
root, Tilia 2-year stem, lateral root origin, Zea prop root, root hairs, typical monocot and dicot stem, typical monocot and dicot leaves, Zea root set 3-day tip, Zea root set 3-day root and Zea root set 6-day root were prepared. 2) A slide of sambucus bark was placed on the stage and was adjusted to focus on the specimen by using the microscope. 3) The features of the sambucus bark was observed by using the power lens of 4x, 10x and 40x of the light microscope to get a better figure. 4) The slide of the sambucus bark was observed, drew and labelled the features on the paper as seen under the microscope. 5) The same procedure from 5.2 until 5.4 was repeated for each slide or sample that had been prepared in the laboratory.
DISCUSSION The purpose of this experiment is to identify the function of plant tissues
and types of roots, stems and leaves. Besides, to describe the characteristic and functions of plant tissue. As in other organisms, the basic structural and functional unit of plant is the cell. Plant cells are organized into tissue. A tissue is a group of cells that forms a structural and functional unit because simple tissues are composed of only one kind of cell. While, group of cells having common origin, similar structure and performing a definite function is called a tissue. Tissues are found in plants and animals. Plants and animals are made up of many different kinds of tissues. Different types of tissues have distinctive architecture best suited for what they do. Plant tissues can be grouped into four types: ground, vascular, dermal and meristemic tissue. While, basic vascular plant parts are roots, shoots, stems, and leaves. In short, plants evolved roots and shoots. Shoots, in turn, can develop stems and leaves. Roots are branched, underground structures that serve two major functions. First, somewhat obviously, roots firmly anchor the plant to a fixed spot. Once a plant takes root and begins to grow in an area with good access to moisture, soil nutrients, and light, it pays to stay. Second, roots serve as transport systems, allowing the plant to suck up water and dissolved nutrients from the soil to support the plant’s growth. Roots have specialized parts that develop from the three major types of plant tissue: ground, dermal, and vascular. Stems are sturdy structures that grow in order to give a plant a fighting chance to spread its leaves in the sun. Stem growth can add to the plant’s height, broaden the area covered by the leaves, or even direct growth from a dark area toward one with more light. To provide mechanical support for a growing plant, stems need to be strong. To help move water and nutrients to the furthest reaches of the plant, stems are stuffed with little transport pipes in the form of xylem and phloem. Leaves are the original solar panels, capturing energy from sunlight in a biochemical process called photosynthesis. The cells within leaf tissues are hectic with biochemistry, importing water and nutrients to support their frantic work, and exporting sugar to provide energy to the remainder of the plant. The import/export business conducted by the leaves is supported by xylem and phloem
Based on the experiment, specimen of root hairs done be observed under compound microscope. The root hairs are simple, unbranched trichomes that increase the surface area of the root epidermis (which comes into contact with soil) for more effective water and mineral absorption. The epidermis also contains special outgrowths, or hairs. Called trichomes, which occur in many sizes. Plants that tolerate salty environments such as the seashore often have specialized trichomes on their leaves to remove excess salt that accumulates in the plants. The presence of trichomes on the aerial parts of desert plant may increase the reflection of light off the plants, thereby cooling the internal tissues and decreasing water loss. Other trichomes also have a protective function. Therefore, root hairs increase the absorptive surface of the root tremendously. Root hairs can be classified under epidermis tissue where epidermis tissue consists of epidermal cells, guard cells, and trichomes are presence in root hairs. The epidermis is the outermost layer of cells on stems and roots that have not yet experienced an increase in girth, which secondary growth. It can be considered the plants original equipment. That is, it is the first outer protective coating a plant stem or root will have. Furthermore, it is the only type of dermis found in a plant stem or root that does not undergo secondary growth. In stems, the outer surface is normally covered with a waxy cuticle that reduces water loss and protects the plant from harmful ultraviolet radiation. In roots, where such protection is not necessary the cuticle is often absent, and root hairs emerge from the mature epidermal cells. Vascular tissues are plant tissue consisting of cells joined into tubes that transport water (xylem) and nutrients (phloem) throughout the plant body. Xylem conducts water and dissolved minerals upward from roots into the shoots, while phloem transports sugars, the products of photosynthesis, from where they are made(usually the leaves)to where they are needed - usually roots and sites of growth, such as developing leaves and fruits. In the root, vascular tissues are found in the middle when observed in a cross section. In the stem, vascular tissues are scattered but arranged on a circular orientation. In the leaves, vascular tissues are focused on the petiole and its branches. When seen under a microscope, type of plant tissue is most likely to present a large amount of cells undergoing cell division is most likely meristematic
tissue. Meristematic tissues, when seen under a microscope, contain a large number of cells undergoing mitosis.
Meristematic tissues are the ones responsible for the
creation of new organs needed in the plant leaves, stems or roots. They are classified into two parts based on their location: apical and lateral meristems. Apical meristems are located at tips of shoots and roots, and are responsible for primary growth. Lateral meristems are responsible for the thickness of a plant, and usually easily noticeable on the barks and stems of a plant. These plant tissues altogether form the three major organs of a plant: root, stem, and leaves. Roots, stems, leaves, and fruits are organs because each is composed of all three tissue systems. A root is a multicellular organ that anchors a vascular plant in the soil, absorbs mineral sand water, and often stores carbohydrates. A stem is an organ consisting of an alternating system of nodes, the points at which leaves are attached, and internodes, the stem segments between nodes, which support the leaves and reproductive structures. A leaf is the main photosynthetic organ of a vascular plant, although green stems also perform photosynthesis. The tissue systems of different plant organs form an interconnected network throughout the plant. For example, the vascular tissue system of a leaf is continuous with the vascular tissue system of the stem to which it is attached, and the vascular tissue system of the stem is continuous with the vascular tissue system of the root. A good example of this is the three basic tissue patterns found in roots and stems which serve to delineate between woody dicot, herbaceous dicot and monocot plants.
POST LAB QUESTION
1) Referring the slide of root hairs, do they originate all the way down to the root cap ( Yes or No)? Yes. This is because the outer area of the bottom of the root protects other root tissues as the root continues to grow into the soil.
2) Examine the root hairs carefully. What happens to their length as you observe them at increasing distance from the root tip? They become longer.
3) The youngest root hairs are the shortest. What does this imply regarding their point of origin and pattern of maturation? Root hairs or absorbent hairs is a tubular outgrowth of a trychoblast, a hair-forming cell on the epidermis of a plant roots. They are mainly found in the region of maturation of the root, and not the zone of elongation because ny root hairs that arise are sheared off as the root elongates and moves through the soul. Root hair cells vary in between fifteen and seventeen micrometers in their meter, and eighty to 1,500 micrometers in lengths.
4) Beneath the epidermis find the relatively wide cortex, consisting of parenchyma cells that contain numerous starch grains. Based on the presence of starch grains, what would you suspect one function of this root might be? It is responsible for the transportation of the materials into central cylinder of the root through diffusion and may also be used for food storage in the form of starch.
5) Do you find any starch grains in the cortex of the corn stem? Yes, because Starch grains are small granules found in the leaves, roots, stems, fruits and seeds of plants
6) Does the spongy mesophyll contain any chloroplasts (Yes or No)? Yes, spongy mesophyll contains many chloroplast. most photosynthesis takes place in palisade cells. Spongy mesophyll also captures light and makes food.
7) What is one function that occurs within the spongy mesophyll? spongy mesophyll is the air spaces in a plant that allow air to diffuse among the cells which are producing and releasing both CO2 and O2, the area where gas exchange occurs.
8) Is the lower epidermal layer covered by a cuticle? Yes, the cuticle covers both the upper and lower parts of the leaf epidermis, made mostly of lipids and waxes. The cuticle tends to be thicker on the top of the leaf, since that's the part that's most exposed to the sun. The cuticle protects the leaf's photosynthesizing cells from danger, such as bacteria, fungal spores, viruses and other disease-causing dangers. The cuticle also protects the leaf's photosynthesizing cells from environmental toxins, excessive ultraviolet radiation and too much water loss.
9) Compare the abundance of stomata within the lower epidermis with that in the upper epidermis. Which epidermal surface has more stomata. All surfaces of the leaf have some amount of stomata for regulating gas exchange for photosynthesis. However, the lower epidermis which is the underside of the leaf have many of it, because it is more often in the shade and when it is cooler, which means evaporation wants to take place as much.
10) Look at the mesophy11 of the leaf. Draw and label it in Figure 11. Is the mesophy11 divided into palisade and spongy layers (Yes or No)? Yes, Mesophyll can then be divided into two layers, the palisade layer and the spongy layer
CONCLUSION
According to our data, there are four different types of plant tissues namely; meristematic, epidermal, vascular and ground tissue. These types of plant tissues have different functions. The cell of each type varies in size, shape, behaviour and composition. Meristematic tissue, it is in this region where new cells are produce. Dermal tissue provides a protective cover for the entire body of a plant. Ground tissue is responsible for the plants metabolic functions. Vascular tissue transports materials like water and nutrients between the root and the shoot system. They are arranged finely in the regions of the plants organ. For example in roots, stem and leaves the arrangements of these tissues are the same. The dermal tissue is located on the outer part, ground tissue is between the dermal and vascular tissue and the meristematic tissue has three main types the apical meristem that occurs in the tips of stems and roots, intercalary meristem takes between the tip and base of stems and leaves and lateral meristem occurs at the side of stems and roots. Therefore, the purpose of this experiment are achieved.
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