nps31C7 - Biology 05B Winter Quarter 2010 Lab 3 page 1...

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Biology 05B – Winter Quarter 2010 Lab 3 – page 1 PLANT ANATOMY Contents: Topic Page I. Introduction 1 II. External morphology 2 III. Roots 2 IV. Stems 4 V. Leaves 6 VI. Seedlings 8 A central theme in biology is that there is a close correlation between structure and function. That is to say that through the process of evolution, organisms have attained a structural organization that facilitates the various life-supporting functions that an organism must perform. This theme is particularly evident in higher plants. Among the fundamental processes performed by plants are the acquisition of water and nutrients from the soil, the translocation of these materials throughout the plant body, the photosynthetic reduction of CO 2 , and the redistribution of this photosynthate throughout the plant. As an aspiring biologist, you should already be somewhat familiar with some of the relationships between these processes and the structure of the plants around you – at least at the level of the commonly recognized plant organs (i.e. roots, stems and leaves). The soil is mined for water and nutrients by a highly branched root system. Erect stems serve as a pathway for the movement of translocated materials as well as provide a scaffolding for leaves so that they can efficiently intercept sunlight. Leaves often have a high surface to volume ratio to facilitate the gas exchange required for photosynthesis. In today’s lab we will study the relationships between the physiological phenomena mentioned above and higher plant structure in more detail. After a brief introduction to the external form of higher plants, where some of the terminology to be used later will be defined, the internal organization of the major plant organs will be examined. Before beginning, it is necessary to remind you of a portion of the hierarchy of biological structure as it applies to plants. The fundamental unit of life is the cell. Groups of cells that are specialized for a common function are called tissues. In plants, groups of tissues that work together in a more generalized common function are referred to as tissue systems. There are three of these tissue systems. They are: the dermal tissue system, which covers the plant surface; the vascular tissue system, which most often occupies the more internal parts of the plant, and the fundamental or ground tissue system which fills the space between the dermal and vascular systems. Each of the plant organs; root, stem, leaf, (and flower); contains all three tissue systems. Further, the tissue systems of each organ are continuous throughout the plant. As mentioned above, we will be looking at the anatomical organization of roots, stems, and leaves with the intent of learning how the structure of these organs correlates with two interrelated aspects of plant function: the movement of solutes and water throughout the plant and the exchange of gasses between the plant’s photosynthetic tissues and the atmosphere. What is expected is that you
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nps31C7 - Biology 05B Winter Quarter 2010 Lab 3 page 1...

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