Lab K: Leaf Form and Function

Figure 1: CAM leaf anatomy of a Bromeliad species.
This bromeliad has unpigmented stripes on its leaves.
(courtesy of J. Cheeseman, PB 234)

Photosynthesis - C3, C4, and CAM Regulation

Variations in Photorespiration - Discusses differences between C3, C4, and CAM plants.

Leaf Structure - includes a cross section picture, as well as epidermal views of stomata

Carnivorous Plant Database - Learn more about the unusual leaf modifications found in many of these plants.

Plant Adaptations - Includes discussion of leaf adaptations.

Leaf Tissues - Provides detailed coverage of the different types of cells that you might find in your leaf cross sections. See the section on Mesophyll for details about C3 and C4 plants.

Zea mays (corn) leaf - also see the closeup of a vascular bundle

More Examples of Leaf Sections: (from PB234 website, J. Cheeseman)

• Vanilla Orchid (a CAM plant) - See also slide set #2. Perhaps the most obvious characteristic is the infrequent chloroplasts in the mesophyll cells, and the accompanying large vacuoles. Perhaps vanilla's success lies in it high capacity for malate storage for CAM photosynthesis.
• Epidendron sp. (an orchid with CAM photosynthesis) - See also slide set #2 and slide set #3. According to her, the leaf is "boring". I have assured her that this only reflects its CAM attitude toward life, and that boring is appropriate in this case. And... compared to vanilla, it is just wonderfully exciting! Compare the two, especially for the numbers and placements of veins and the presence/absence of fiber cap support structures. The Epidendron has a much thinner leaf with more prominent veins than the vanilla.
• Strangling Fig (Ficus benghalensis) - Figs have a number of interesting adaptations, including the multiple upper epidermis, the bundle sheath extensions of the veins and the placement of the veins relatively close to the lower epidermis. See also: Ficus slides #2.
• Anthurium sp. (a C3 plant) - see also slide set #2 and slide set #3. Her work resulted in three composite pictures of leaves, and one of the petioles. As we have discussed in class, the petiole structure here shows both the strength needed to support the long petiole and heavy leaf a long way from its attachement point, and the "flexi-straw" structures near the leaf blade itself that allow the leaves to move in the wind. Heidi also made epidermal sections and finger nail polish replicates of the epidermal surface to show the placement of the stomates and the subsidiary cells.
• Water Hyacinth - This is the floating water plant that was in the lab several weeks ago. It has outpockets from its stem which help it float.
• Heliconia sp. - The leaves are intersting for the upper epidermis especially, and for the way the epidermis and mesophyll morph around the more major veins. The petiole is interesting because of the large lacunae or aerenchyma (what would that be for in a plant that isn't submerged?) Note that the upper surface is flatter than the rest of the petiole, and the way that the bundle sheaths around the veins re-inforce the petiole. The needles are "raphides", Ca-oxalate. They are normally packaged in vaculoes in specialized cells. Because they are so unpleasant to animal gums, they can be a fairly effective and cheap way to deter herbivores.
• Allspice (a C3 plant) - see also slide set #2. a pioneer tree that could grow under the conditions found in Central America. If you are looking at all the pictures on this page, you should particularly compare the allspice epidermal layers (numbers and sizes of cells in the layers) with those of other species, and the support structures of the veins between species. Allspice has a pretty clear arrangement of palisades and spongy mesophyll tissues, with some very definite contrasts to some of the other species.
• Crossandra sp. (a C3 plant) - Notice the distinct spongy and pallisade mesophyll layers.
• Phyllanthus sp. (a C4 plant) - Notice the bundle sheath and mesophyll cell arrangement around the vascular tissue (lower right photo). Also, a nice epidermal peel showing stomata.
• Chamaedorea sp. - Nice epidermal peels of upper and lower epidermis.
• Achmea - These slides show interesting adaptations, such as sunken stomata and glandular trichomes.