Laticifers are some of the most peculiar elements of the plant body and are found in a restricted number of   famous or infamous families and genera. Their infamy stems from the poisonous or addictive nature of their contents. However, the soothing qualitiies of the latex from the opium poppy led to the development of powerful pain killers like morphene which have made life and death more tolerable for seriously afflicted patients. Laticifers are long cells or vessel-like series of cells permeating various tissues of the plant. They contain variously colored, often milky juice called latex.

Galery of Familiar Plants which have Laticifers.

I have grouped these according to Families. I am not concerned that you learn these families or these plants by name. I want you to recognize plants that you see on campus and elsewhere in Hawaii. If you develop an interest in these plants you will want to learn about them for your own fulfillment.

Apocyanaceae

Cascabela thevetia	Cerbera manghas Note the latex oozing from the X cut into the fruit.		Stemmadenia littoralis
Plumeria obtusa		Nerium oleander

Asclepiadaceae

Hoya bicarinata

Calotropis gigantea

Euphorbiaceae

Aleurites moluccana		Jatropha integerrima
Acalypha hispida	Euphorbia pulcherrima Euphorbia splendens

Moraceae

Ficus religiosa

Artocrpus altis Ficus carica

Papaveraceae

Argemone glauca

Papaver orientale

• Examine the color of  latices from various plants which may include Poppy (Papaver); Papaya (Carica papaya); Breadfruit (Artocarpus sp.);  Euphorbia pulcherrima (white); Nerium oleander (colorless);  Ficus sp. (milky white);  Calophyllum inophyllum (yellow),  (Casabella thevetia) or  Plumeria.

• Make Longitudinal sections of stems and petioles containing laticifers.

• Stain these with IKI or Sudan

Laticifers in olona (Touchardia latifoliolata):

This plant produces incredibly strong "fibers" which were used by ancient Hawaiians to fashion their capes and helmets. Olona also produced the finest rope for sailing vessels and was unparalleled for its strength and durability until the introduction of synthetic polymers. The "fibers" are actually laticifers with incredibly thick walls.

• Make transverse and longitudinal sections of young stems.

• View unstained and look for latex.

• Examine them with your polarizers.

• Stain with Toluidine Blue. Are the "fibers/laticifers" lignified?

Low Mag. View of Olona Stem seen with Polarized Light: Where are the thick-walled cells?	Unstained Laticifers at High Mag: Note the orange Latex in one laticifer, and the thick, translucent walls
Longitudinal section of Olona stem viewed with crossed polarizers: What does the birefringence tell you about these cells?	Olona Laticifers stained with Toluidine Blue

NECTARIES

• Locate the nectariferous tissue and vascular bundle first in fresh material, then look at the prepared slides.

• The transverse sections of the receptacle show:

1. Only phloem occurs in the smallest bundles arranged in an area around the opening.

2. Phloem ends in densely cytoplasmic cells.

3. Larger, more vacuolate cells subtend the epidermis.

4. Epidermis and some other cells have yellow, granular contents.

5. Epidermis near the largest bundle has stomata but no cuticle.

6. Epidermis near the smaller bundles has cuticle but no stomata.

Crinum asiaticum

The nectariferous cells are the dense, small cells in the lower end of the floral tube wall, just above the ovary.

• Carefully cut cross-sectional chunks off the tube, starting at the top, to see how much of the tube (of an upright flower) is filled with nectar.

• A median longitudinal cut should reveal the cells secreting the nectar.

Acerola

• Locate the floral nectaries with a dissecting scope.

Ring Nectaries

Many flowers have a "disk" or ring nectary around the base of the gynoecium, e.g., species of Asystasia, Alamanda, Convolvulus and Cucumis

• Examine the prepared slide of a median longitudinal section of Cucumis and find the nectary.
  
  Can you deduce where the nectar is secreted?
  
  Does the epidermis have a cuticle in this region?
  
  Are both xylem and phloem present in the nectariferous tissue?
  

  Male & Female Cucumber (Cucumis)  Flowers

  Long section of a Cucumber Ovary

• Locate similar nectaries on the corresponding living flowers.

Allamanda sp.

Argyreia nervosa (Convolvulaceae)

Abutilon

The floral  nectaries of various species from  this genus and family (Malvaceae) have been studied more than those of most plants.

They are located on the upper surface of the base of the sepals, the secretory apparatus consists of closely packed hairs along with underlying nectariferous tissue.

• To see nectar secretion in action, cut a thin transverse section of a sepal through this region and mount in immersion oil.

• Look for small droplets of nectar at the tips of the hairs, and watch them grow.

• Look also at the prepared slide and locate the large
  
  mucilage cells, druse cells & vascular bundles.
  
  The vascular bundles are on the abaxial (lower) side, among, the densely stained nectariferous cells.
  
  Note that sieve tubes branch from the main vein and permeate the nectariferous tissue.

Extrafloral Nectaries

These usually occur somewhere on leaves, but may be located on stems or bracts.

Ricinus communis

Find the two large nectaries on the petiole of a fresh leaf.

• Observe a prepared slide that shows the densely stained nectariferous tissue.

• Locate the tracheary elements and determine how close they come to the epidermis. Can you find sieve elements? Do they come closer to the epidermis? Note how the (secretory) epidermal cells are much denser than the two cell layers just underneath. Note also the thick cuticle covering the epidermal cells.

• TIME Permitting - Find other examples of extrafloral nectaries.

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  Kuikui Leaf (near base of lamina),

  Norantea (floral bracts modified into large orange tubes)