Submitted by Tyler Yates In lab we examined various roots from two different dicot plant specimens. Pisum Sitivum (pea), and Vicia faba(bean). Cross sections were prepared and examined under a compound microscope. The picture below on the right is a cross section of Pisum Sativum and an annotated image to the left identifies the structural internal components. Notice the external root hairs stained dark blue surrounding the epidermis. internal to the epidermis is the cortex made up of the larger clear parenchyma cells of the ground tissue. The group of cells in the middle is the stele, or procambium. The procambium includes the vascular tissues as well as the pericycle; surrounded by the endodermis. The pericycle, in dicot roots, gives rise to lateral roots, cork cambium, and portions of vascular cambium. Notice that the pith is absent in dicot roots .
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By: Chelsea Maddox Just this last week in lab on Thursday, February 16th we took a look at structure of roots and their external features. From what we have learned so far about roots is that they have many functions. One: they anchor the plant to a substrate. Two: absorb water and minerals. Three: they conduct water, mineral, and carbohydrates. Four: roots store the carbohydrates while playing an additional role in asexual reproduction. The external features and structure of roots is very important because they are associated with how they carry out the above functions. Plants have two types of branched root systems. One being a fibrous root system and another being taproot system. Angiosperms have been classified into two major groups known as monocots and dicots. The monocots is associated with a fibrous root system because they are commonly short-lived so they are composed of adventitious, branched roots. So you've probably guessed by now, dicots are associated with the taproot system because the plants strive to live longer. The taproot system has a primary root that develops as a taproot which then gives rise to secondary, adventitious, branched roots. The images I am going to show below are of corn (Zea mays), a monocot with a fibrous, adventitious root system.
Unlike corn (Zea mays), a broad bean plant (Vicia faba) is a dicot with a taproot root system. Even though the root system isn't fibrous, it is still considered to have adventitious, branched roots. Below are some images I took in lab on Thursday, February 16th of the mature broad bean plant. Unfortunately, I am unable to label the close up view of the dicot broad bean with the taproot system because it just looked like mess because the picture I have of the root are bunched together too tight. However, to the left, I have uploaded an image of the broad bean root system labeled for a better understanding of the difference between monocot and dicot root. Numbers 4 and 5 I feel do a great job pointing out which part is what in these figures. One thing I found interesting in class and I was highly encouraged to present within this blog is the unique nitrogen-fixing organs that result from a symbiotic interaction between the plant and nitrogen fixating bacteria known as root nodules. Most legumes result in infection by bacteria of the host-plant root. More information of how the process of infection begins you can gather from recommended reading (Ch. 29, pgs. 693-700 in Raven's Biology of Plants). Assuming the recommended reading was done before lecture on February 9th, you may remember reading about the two different types of root nodules. They can be distinguished by either indeterminate or determinate. Indeterminate root nodules are elongated and cylindrical due to the presence of the meristem. However, the determinate root nodule is presented in spherical form due to the lack of the persistent meristem. The image I will be showing you below is of indeterminate root nodules on the roots of a mature broad bean plant. These nodules on the mature broad bean are common of the legume (Fabaceae) family. "Legumes secrete compounds called flavonoids from their roots, which in turn trigger the secretion of nod factors in the rhizobia. Coming full circle, the nod factors spark a reaction in the legumes, causing the roots to swell and form the nodules you see here. It is within these nodules that rhizobia live in harmony with their host plant."
Read more at http://www.gardenbetty.com/2012/11/a-look-at-legumes-rhizobia-and-root-nodules/#ZV650Ij8EhVTtrGs.99 The coolest part about lab on Thursday was getting to cut open the root nodule on the broad bean plants while examining it under the dissecting microscope. When cut open, the nodule represented a pinkish/red color (pictured below). The nodule having the color inside represents the presence of leghaemoglobin which means the nodule is active and is fixing a lot of nitrogen for the plant. FUN FACT: the redder the nodule, the more ACTIVE it is! Submitted by Emily Burkhart I'd like to start off by saying ♥Happy Valentines day♥ to everyone! In this blog post we'll explore dicot, pine and simple leafs. All the information below has been gathered from lab on Tuesday and Thursday of week 5. Dicot leafBroad Bean Vicia Faba plant was used in class for a look at the cross section for a dicot leaf. There are two groups that all flowering plants or angiosperms were formerly divided into. How they were decided which group they belonged in depended on their characteristics. These two groups are monocots and dicots. The images below are images of the plant and the cross section of the plant broad bean. When looking at the difference between monocots and dicots there are 6 characteristics to look at; seedpod, flower, stem & roots, leaves, germination, and seeds. Here is a link to a really good website that gives more information at distinguishing these differences : http://theseedsite.co.uk/monocots2.html The above slide was taken in class at the magnification of 100x. It is the cross section of a broad bean leaf Simple leafTo the left are 16 examples of what some simple leaves can look like, but what does it mean to be a simple leaf? A simple leaf: An undivided leaf; as opposed to a compound leaf. The blades are not divided into distinct parts, although they may be deeply lobed. Below are some examples of common simple leafs. The two images were from: http://biology.tutorvista.com/plant-kingdom/leaf.html This is also a really good website for a quick summary and run down on comparing leaves FUTURE LOOK > Later in the blog, compounds leaves will be discussed and looked at when comparing simple and compound leaves, but below is a really good video for when identifying the differences and what to look for! Pine leafThis is my favorite kind of pine, Knobcone pine, Pinus attenuata. Knobcone pines is a tree that grows in mild climates on poor soils. It ranges from the mountains of southern Oregon to Baja Califonia with the greatest concentration in northern California and the Oregon-California border. ________________________________________________ FUN FACT: It's actually incorrect to call them pine cones because cones can come from fir trees as well. So they are actually just known as cones and depending on the tree it comes from depends on if it is a pine-cone or a fir-cone. There are around 100 pines, all of which are characterized by an arrangement of leaves that is unique among living conifers. After a year to two years is when the pine will produce needle leaves in a bundles, or fascicles which contains a certain amount of leaves depending on the species. These fascicles are wrapped at the base in small scalelike leaves, and are actually short shoots in which the activity of the apical meristem is restricted so the fascicle of needles in a pine morphologically is determinate. Fascicle: A bundle of pine leaves or other needlelike leaves of gymnosperms; an obsolete term for a vascular bundle. The two cross sections above of the pine leaf were taken at the magnification of 100x. Both images were taken during lab.
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