- -  AGRICULTURE CORE CURRICULUM - -


(CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE

 (CLF6200) Unit Title: PLANT PHYSIOLOGY AND GROWTH

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 (CLF6202)  Topic: GROWTH                   Time     Taught in Year(s) 
                     PATTERNS                 1 hour        3 and 4  
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        Topic Objectives: Upon completion of this lesson the student will 
        be able to:

        Learning Outcome #:

          (C-14) - Trace the stages of development (using bean, pea,
                    onion, and corn plants) from germination to the stage
                    of first true leaves. Compare and contrast the types
                    of growth. 

          (C-15) - Describe the life cycle of a dicotyledonous plant from 
                    seed to seed production. 

        Special Materials and Equipment: Test plot or planters, with soil 
                    mixes and seeds of bean, corn, onion, pea, and radish.

        References: Hartmann, H. T., Flocker, W. J., & Kofranek, A. M. 
                     (1981). PLANT SCIENCE: GROWTH, DEVELOPMENT, AND 
                     UTILIZATION OF CULTIVATED PLANTS. Englewood Cliffs,
                     NJ: Prentice-Hall.

        Evaluation: Quiz by instructor

TOPIC PRESENTATION: GROWTH PATTERNS

A. Classification

   1. Nearly all economically important plants used for feed, fiber, food,
       shelter, and recreation belong to the Division Anthophyta (flowering 
       plants) and the Division Coniferophyta (conifers, such as pine).

   2. The Anthophyta includes two classes of plants: the Monocotyledonae 
       (monocots) and the Dicotyledonae (dicots).

       a. The monocots include 50,000 species of plants.

           1) These are formed in more than 40 families, including the 
               grasses, lilies, orchids, irises, and palms.

           2) The grasses and palms together provide the main source of 
               food for most people on earth.

       b. The dicots include approximately 200,000 species.

           1) These are grouped into more than 250 families which include 
               the broad-leaf trees, roses, peas, mustard, and sunflowers.

           2) Many important agricultural crop plants are included in this 
               subclass.

B. Several traits distinguish monocots from dicots:

   1. The monocot embryo has one cotyledon; the dicot embryo has two 
       cotyledons. 

       a. A cotyledon is a leaf that is specialized for absorbing food 
           within a seed.

   2. Monocot leaves have many parallel veins of similar size (parallel 
       venation). Dicot leaves have a main vein that forms many smaller
       branch veins, each or which forms still smaller branches (netted 
       venation).

   3. Monocot stems have vascular bundles scattered throughout the 
       cross-section of the stem. Dicot stems have bundles arranged in 
       a ring.

   4. Many dicots have a vascular cambium that adds thickness to stems and 
       roots. Very few monocots have a vascular cambium.

   5. Most monocots have flower parts in multiples of 3. Most dicots have 
       flower parts in multiples of 4 or 5.

   6. Most monocots have a fibrous root system, with many roots of similar 
       size and no one root that is much larger. Most dicots have a
       taproot system, with one large root and many smaller branches.

   7. Most monocots have strap-shaped leaves, whereas dicot leaves usually 
       have broader shapes (hence, dicots are often called broad-leafed 
       plants).

C. Grasses, including cereals, have additional distinguishing features:

   1. Their stems are usually hollow, with a round cross-section and 
       conspicuous, solid nodes.

   2. Each node bears one leaf, and the leaves at successive nodes grow 
       from opposite sides of the stem.

   3. Each leaf has a sheath that clasps the stem, and a strap-like blade 
       that extends out from the stem and grows at its base.

   4. The flowers are inconspicuous and can easily be overlooked. They
       are pollinated by wind.

   5. The sepals and petals are highly modified, as glumes, lemma, and 
       palea -- structures that aid in dispersing and planting seeds.

   6. Many grasses spread vegetatively by underground rhizomes.

   7. Some of these features occur in other monocots as well.


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         ACTIVITY: 
 
         1. Provide seeds of monocots and dicots (use bean, pea,
             onion, and corn).

         2. Assign students to compare and contrast the development
             of these four plants from germination through the 
             formation of the first true leaves.

         3. Assign students to make written observations of the leaf
             and flower structures of each as they grow.

         4. Plant a test plot of dicotyledons and observe the
             plants from germination through seed formation. 
             (Beans, peas, and radishes work well for this.)
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12/14/90 PJK/sg

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