Examining Primary and Secondary Growth and Movement of Sugar and Water
Examining Primary and Secondary Growth and Movement of Sugar and Water
As a novice to plants, I have noticed that there is more this things that happen behind the scene that I was not aware of. For example; animals eat plants and we eat animals that eat the plants, plants also creates something very important to humans and animals……oxygen. Without plants our ecosystem would surely collapse.
The three types of plant cells are parenchyma, collenchyma, and sclerenchyma.
Parenchyma is a tissue typically composed of living cells that are thin-walled, unspecialized in structure, and therefore adaptable, with differentiation, to various functions. The main functions of parenchyma cells of roots and stem is the storage of food (e.g. starch) and water, the intercellular air spaces permit gaseous exchange. The parenchyma is found in the leaves.
According to “Collenchyma” (n.d.), “Collenchyma is a tissue and is mainly found under the epidermis in young stems in the large veins of leaves. The cells are composed of living, elongated cells running parallel to the length of organs that it is found in. Collenchyma cells have thick cellulose cell walls which thickened at the corners.” (para. 1)
Sclerenchyma is a primary wall and a thick secondary wall that is almost always lignified. These walls are elastic: They can be deformed, but they return to their original size and shape when the pressure or tension is released. Sclerenchyma serves the function of support in plants.
Cross –section of a Stem
Cutin – A polymer of fatty acids that is water impermeable; it forms a layer (cuticle) on the epidermis.
Cuticle – A layer of cutin on epidermal cells; the cuticle reduces water loss but also unavoidably restricts the entry of carbon dioxide.
Epidermis – The outermost layer of the plant primary body, covering leaves, flower parts, young stems, and roots.
Guard cells – A pair of epidermal cells capable of adjusting their size and shape, causing the stomatal pore to open when they swell and close when they shrink.
Stomata – the intercellular space between guard cells through which carbon dioxide and water are exchanged and sometimes used to mean “stomatal complex,” the stomatal pore plus guard cells plus associated cells.
Cortex – In stems and roots, the primary tissue located between the epidermis and the phloem.
Vascular Bundle A column of vascular tissue, typically both xylem and phloem together, but in leaves sometimes consisting of only one or the other.
Lenticels are found on the stem or trunk of plants. Lenticels are a type of spore. They serve as a site of gas exchange on the plant (place where oxygen and carbon dioxide can enter and exit). Lenticels are also, unfortunately, a site where pathogens such as fungi, bacteria, and viruses can enter the plant. See Figure 1
Figure 2 shows a picture of a stem labeled with the nodes, internodes, apical meristems, leaf buds and flower buds.
According to “Apical Meristem: Definition & Function” (2003-2015), “Apical meristem causes the plant to grow up and down to get longer. This kind of growth is called primary growth. When a plant grows ‘out’ or gets thicker, it’s called lateral or secondary growth. Both directions of primary growth are important, since it stretches the plant’s leaves to light and pushes its roots deep below the ground to seek out water and anchor the plant”.(para. 2)
According to “Tilia Stem Cross Section” (n.d.), “a cross section of secondary growth in a woody species. The primary xylem and phloem, secondary xylem and phloem, fascicular cambium, and interfascicular cambium”. (para. 1).
There are two additional meristems:
Vascular cambium, which produces secondary xylem and secondary phloem. This is a process that may continue throughout the life of the plant. This is what gives rise to wood in plants. Such plants are called arborescent. This does not occur in plants that do not go through secondary growth (known as herbaceous plants). Cork cambium, which gives rise to the periderm, which replaces the epidermis.
Water, Sugar, and Mineral Transport in Plants consist of the following:
Symplast – Most plant cells communicate with their neighboring cells, transferring
water, sugars, minerals, and hormones at least. This movement
occurs by a variety of mechanisms. First, all living cells are interconnected
by plasmodesmata, the fine cytoplasmic channels that pass
through primary cell walls. All of the protoplasm of one plant can
be considered one continuous mass.
Osmosis – the process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane
Transport Vesicles – Small membrane-bounded organelles that carry secretory and membrane proteins in both directions between the rough endoplasmic reticulum (ER) and the Golgi complex, and from the Golgi to the cell surface or other destination
Apoplast – acts as a series of channels and spaces that permit the rapid diffusion of gases, which is necessary because plants do not have lungs.
Transfer Cells – are parenchyma cells that mediate short- distance transport of material by means of a large, extensive plasma membrane capable of holding numerous molecular pumps.
According to “Plant Growth Factors: Photosynthesis, Respiration, And Transpiration” (2013), “Transpiration serves three major roles:
Movement of minerals up from the root (in the xylem) and sugars (products of photosynthesis) throughout the plant (in the phloem). Water serves as both the solvent and the avenue of transport.
Cooling – 80% of the cooling effect of a shade tree is from the evaporative cooling effects of transpiration. This benefits both plants and humans.
Turgor pressure – Water maintains the turgor pressure in cells much like air inflates a balloon, giving the non-woody plant parts form. Turgidity is important so the plant can remain stiff and upright and gain a competitive advantage when it comes to light. Turgidity is also important for the functioning of the guard cells, which surround the stomata and regulate water loss and carbon dioxide uptake. Turgidity also is the force that pushes roots through the soil”. (para. 3).
Apical Meristem: Definition & Function. (2003-2015). Retrieved from http://study.com/academy/lesson/apical-meristem-definition-function-quiz.html
Biology4Friends. (n.d.). Retrieved from http://www.biology4friends.org/plant-microscope-exercise.html
Collenchyma. (n.d.). Retrieved from http://www.botany.uwc.ac.za/sci_ed/grade10/plant_tissues/collenchyma.htm
James D. Mauseth/University of Phoenix. (2014). Botany/An Introduction to Plant Biology. Retrieved from James D. Mauseth/University of Phoenix, BIO204 website
Lenticels on a Tropical Tree. (n.d.). Retrieved from http://www.botgard.ucla.edu/html/botanytextbooks/generalbotany/barkfeatures/b0256tx.html
Parenchyma. (n.d.). Retrieved from http://www.botany.uwc.ac.za/sci_ed/grade10/plant_tissues/parenchyma.htm
Parenchyma: Plant Tissue. (2015). Retrieved from http://www.britannica.com/science/parenchyma-plant-tissue
Plant Cells and Tissues Plants. (n.d.). Retrieved from http://www.bio.miami.edu/dana/226/226F09_5print.html
Plant Growth Factors: Photosynthesis, Respiration, and Transpiration. (2013). Retrieved from http://www.ext.colostate.edu/mg/gardennotes/141.html
Plant Structure, Growth, and Development. (2015). Retrieved from http://www.slideshare.net/jayswan/chapter-35-presentation
Tilia Stem Cross Section. (n.d.). Retrieved from http://www.biosci.ohio-state.edu/~plantbio/osu_pcmb/pcmb_lab_resources/pcmb101_activities/scndry_grth/scndry_grth_tilia_stem_cs.htm
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