Leaf Lab Review - Lab Exam 2

Slide 1:
Simple Leaf		 The blade of a simple leaf is not divided into individual sections (leaflets) although it may be deeply lobed.  A simple leaf consist of a single continuous blade and the petiole.  The axillary bud is located at the base of the petiole where the petiole attaches to the stem.
Slide 2:
Palmately Compound Leaf		 The blade of the palmately compound leaf is divided into two or more individual sections (leaflets).  In a palmately compound leaf each leaflet is attached at the tip of the petiole rather than being spaced along the petiole as in pinnately compound leaves.  Axillary buds are not found at the point of leaflet attachment to the tip of the petiole, rather there is a single axillary bud located at the point where the petiole attaches to the stem.
Slide 3:
Pinnately Compound Leaf		 The individual leaflets of a pinnately compound leaf are spaced along the length of the petiole.  Note the location of the axillary bud at the base of the petiole where it attaches to the stem.
Slide 4:
Alternate Leaf Arrangement		 Leaf arrangement is determined by the number of leaves found at each node.  In alternate arrangement there is only one leaf per node, usually alternating from one side of the stem to an other as on moves from node to node.
Slide 5:
Opposite Leaf Arrangement		 In opposite leaf arrangement there are two leaves per node.  Leaves are usually located on opposite sides of the node.  Whorled leaf arrangement has three or more leaves per node which are arranged (whorled) around the node.  We do not have a picture of whorled arrangement, but be able to identify it from a drawing.
Slide 6:
Venation
    Parallel Venation
    Pinnately Netted Venation
    Palmately Netted Venation		 Parallel venation is usually found in long narrow leaves such as grasses or grass- like plants.  Major veins extend the length of the blade with little visible branching.
Pinnately netted leaves have a single main vein, the midrib, which extends the length of the blade.  Smaller veins branch from the midrib.  These veins continue to branch forming a network of veins.
Palmately netted leaves have several main veins which originate from the same point at the base of the blade where it attaches to the petiole.  The veins radiate from this point like fingers radiating from the palm of the hand.  As in pinnate venation the veins continue to branch forming a network of veins.
Slide 7:
Axillary Buds		 Axillary buds are located at the base of the petiole in the axial (angle) between the petiole and the stem.  Axillary buds can give rise to leave or branch stems.
Slide 8:
Monocot Leaf, Zea Leaf Cross Section		 The mesophyll of Zea is undifferentiated.  Note the large bundle sheath cells and that stoma are found in both the upper and lower epidermis.  Identify and give the function of all labeled leaf structures.
Slide 9:
Dicot Leaf, Ligustrum Leaf Cross Section		 Note the well differentiated mesophyll with a palisade mesophyll on the upper surface and the spongy mesophyll below.  Identify and give the function of all labeled leaf structures.
Slide 10:
Pine Leaf Cross Section		 The pine leaf is well adapted to dry conditions with a thick epidermis with stoma recessed into the into the surface.  Beneath the epidermis is the thick walled cells of the hypodermis which helps reduce water evaporation from the leaf.  The pine leaf has an endodermis inside the mesophyll which is not seen in either of the other leaf types observed.
Slide 11:
Stoma		 Identify the guard cells that both form the stoma and regulate its size.
Slide 12:
Hydrophytic Leaf		 Hydrophytic leaves are adapted to an aquatic existence.   Note that the upper palisade mesophyll is well developed for photosynthesis while the lower portion of the mesophyll is very loosely arranged with considerable open space which helps the leaf float to the surface.  The loosely arranged tissue of the lower mesophyll is aerenchyma.  stoma are located in the upper epidermis.
Slide 13:
Zerophytic Leaf, 200X		 Zerophytic leaves are adapted to arid conditions.   Note the thick cuticle, epidermis and hypodermis on the upper and lower surface of the leaf.  Stoma are recessed deeply into the lower surface of the leaf with numerous dermal hairs in the cavity surrounding the stomata.  This reduces air flow across the stoma surface thus reducing water loose from the leaf.
Slide 14:
Zerophytic Leaf, 400X		 Note the structure of the cavity that contains the stoma.
Slide 15:
Mesophytic Leaf		 Mesophytic leaves are adapted to average conditions.   Our example is the typical dicot leaf, Ligustrum