Group 4 BSBS 1-A Alanan, Nerwell Jean F. Apelido, Rey Dominic V. Baure,Jillane G. Beñosa, Christelle Marie P. Activity #1: Microscopic Study of Some Living Plant Cells I. Introduction The study of the cells is of great importance for us to be able to understand comprehensively all life by starting at the fundamental. The discovery of the microscope has opened up a whole new dimension in science. Its importance is very much appreciated when investigating structures and functions of cells from different organisms since the cell is the basic unit of life. II. Objectives To gain information on the general structure of relatively simple living plant cells. III. Methods A. Mature Trichome Cells: (Cucurbita maxima Duch - squash) Make a temporary mount of squash trichomes or hairs. Put a small drop of water on the glass slide. Place specimen (only a few hairs) and cover with a cover slip over the specimen. Tilt the cover slip over the specimen on the glass slide. Supporting the raised cover slip slowly, examine a living cell under, the high power objective and identify the parts visible. B. Mature Onion Cell: (Allium cepa L.) Make a temporary mount of a strip of onion epidermis. Using a blade, remove the inner layer of epidermis from the concave surface of one of the onion bulb layers. The layer of epidermis should be transparent. Place it immediately in a drop of dilute iodine or Lugol’s solution at the center of a clean glass slide. Be sure that the strip of epidermis is spread out flat.Using toothpicks, we straightened out any folds in the onion skin. Carefully place over the whole mount a clean cover strip. C. Mature Green Leaf Cells of Elodea: (Hydrilla verticellata (Roxb) Hoyle) Take a leaf from an actively growing shoot of Elodea or Hydrilla which has been exposed to bright light or have been pressed hard against the glass slide with the thumb to induce cyclosis or streaming of the protoplasm. Make a temporary mount placing the lower surface of the leaf next to the slide. Observe the arrangement of cells under low power. Find the portion of the leaf where you can see clearly and change to high power. Observe either the cells of the upper layer of the tooth-shaped cells along the margin. D. Mature Epidermal Cells with Chloroplasts and Pitted Cell Walls (Capsicum annuum L. or red sweet pepper) Using a very sharp razor blade, make a very thin section of the epidermis of a red sweet pepper. Mount this in Lugol’s solution and examine under the low power objective. Then switch to high power to observe the canals called pits through thick cell walls. IV. Results/Answers A. Mature Trichome Cells: (Cucurbita maxima Duch. - squash) 1. Under the LPO, how many cells do you see in each trichome? We were able to see three cells in each trichome under the LPO. 2. Where is the nucleus in these cells? The nucleus, which appears to be a dark glob, is located inside the cell and surrounded by clear spaces known as the vacuole. 3. Where is the cytoplasm? The cytoplasm is enclosed inside the cell membrane. Sections of the cytoplasm has these thread-like structures - the cytoplasmic strands - that keeps the nucleus in place. 4. Study Plate IV - The Plant Cell in squash hair. Label all parts seen. Indicate its correct magnification. Total magnification: 100x Cell wall Nucleus Cell membrane Cytoplasmic Strand Vacuole Total magnification: 400x Chloroplasts Total magnification: 40x B. Mature Onion Cell: (Allium cepa L.) 1. Cell wall - transparent, thick-walled delimiting each cell. i. Is it uniform in thickness? Yes, the cell walls are uniform in thickness. ii. What do you call the narrow canals or depressions found at intervals along the cell walls? Plasmodesmata. They are plasma membrane-lined channels that passes through plant cell walls and allows cytoplasmic exchange between adjacent plant cells. It provides passage of ions and small molecules, but also of macromolecules such as RNA or proteins. 2. Cytoplasm - a thin, transparent, finely granular layer, completely lining the cell wall, sides, top and bottom. The center of the cell is occupied by the clear, colorless cell sap which fill the vacuole. i. Can you distinguish the protoplast clearly. Yes, the protoplast can be distinguised. ii. Are plastids present in the cell? Yes, plastids are present in the cell. iii. Are they colored? No, they are colorless. iv. Can you discern cytoplasmic strands? Yes, it can be discern. 3. Nucleus - a rather dense, globular body embedded in the cytoplasm at the side, top or bottom of the cell. Within the nucleus, note the brighter smaller but rounded body or nucleolus. i. How many nucleoli do you observe? Under our observation, we were only able to see one nucleolus. ii. What occupy the spaces in between the cytoplasmic strands? We identified the spaces in between as vacuoles. 4. Label the parts of a mature onion cell shown on Plate III showing all the canals or the plasmodesmata on cell wall. Indicate its correct magnification. Total magnification: 100x Nucleus Plasma membrane Plasmodesmata Cell wall Vacuole Cytoplasm Cytoplasmic Strands Nucleolus C. Mature Green Leaf Cells of Elodea: (Hydrilla verticellata (Roxb) Hoyle) 1. Cell wall - Does each cell have its own wall? Yes, as observed in our specimen. 2. Draw one mature leaf cell of Hydrilla verticellata 70 ml. long. Indicate with arrows the direction of the protoplasmic streaming and get its correct magnification. Total magnification: 100x D. Mature Epidermal Cells with Chromoplasts and Pitted Cell Walls: (Capsicum annuum L. or red sweet pepper) 1. What do you call those rounded colored bodies scattered abundantly all over the epidermis? They are called chloroplasts and they give the epidermis of the bell pepper its red color. Total magnification: 400x Conclusions: 1. Do adjacent cells share a common wall? Yes they do. 2. Of what material is the cell composed? Cellulose, a polymer made out of repeating glucose molecules, composes the cell wall which surrounds the cell. Additionally, lignin also comprises a portion of the cell wall. It provides mechanical support for stems & leaves and supplies the strength and rigidity of the cell wall. 3. How do you account for the apparent presence of the nucleus within central vacuole of some Elodea cells? The nucleus located in the central vacuole of the cell is far more apparent compared to nuclei found in the other parts of the cell. This is due to the high number of chloroplasts found in the cell, which is less abundant compared to the central vacuole. Thus, the nucleus is visible in the central vacuole. 4. Due to circumstances, we weren’t able to record the movement of chloroplasts in the plant cell. Not enough sunlight and stimuli were the reasons. However, we will try to explain it conceptually. i. In what direction does the streaming of cytoplasm in Elodea proceed? The chloroplasts move around the cell’s central vacuole during its streaming. They move in a cyclic manner - either clockwise or counter-clockwise direction. ii. Is the direction of streaming the same in all cells showing it? Not necessarily. Some cells have a clockwise streaming and others have a counter-clockwise streaming. iii. Does the direction of streaming change? No, it remains the same all throughout the streaming. iv. Is the speed of movement the same in all cells? No, they are different. Some cells streams fast while others are slow. 5. Characterize mature plant cells in contrast to young ones. Based on our observations of plant cells, younger cells tend to have multiple vacuoles. Then as they mature, they combine these vacuoles resulting to a large central vacuole that occupies more than 30% of the cell’s volume and as much as 90% of the volume of certain cells.