Lab 2: Vegetative Characters

Objectives for this lab:
  • learn the different root types
  • learn to recognize and name different stem modifications
  • learn to recognize and interpret simple and compound leaves
  • become familiar with leaf shapes, bases, apices, margins, arrangements, forms, and textures and the terms that describe these features
  • learn to recognize different growth forms--herbs, vines, trees, shrubs
  • learn to recognize vegetative features such as thorns, spines, prickles, tendrils
  • examine and learn to recognize different types of trichomes (plant hairs)
  • practice keying with a key that uses vegetative characters
Safety concerns for this lab:  Be careful of plants with sharp parts, don't eat the samples, and be careful where you step when walking on campus.

This lab deals with characters of the vegetative parts of a plant--roots, stems, twigs, and leaves.

Most items have a visual link, but some do not. This topic is covered fully in Vascular Plant Taxonomy by Walters and Keil .

ROOTS

STEM ANATOMY

STEM MODIFICATIONS

GROWTH FORM

DURATION

PARTS OF A LEAF and NODE

LEAF ARRANGEMENT

SIMPLE AND COMPOUND LEAVES

Helpful Hint: In trying to decide where a leaf begins, look for the axillary bud. Everything above the axillary bud is all one leaf.
  
Simple--the blade is all in one piece, though it may be lobed, toothed, etc.

VENATION

LOBING

LEAF SHAPES

There is a bewilderingly large number of terms used to describe the shapes of leaves (or of any other organ, for that matter). In this course, we will stress some of the more commonly-employed terms. Helpful Hint: The prefix ob- means opposite, so for every shape term, a term for the same shape turned the other way around can be created by adding "ob-" to the term. For example, oblanceolate means 'shaped like the tip of lance, broadest at the top and long-tapered to the base.'

APICES AND BASES

A number of terms describe the shape of the apex or base of a leaf. Some of the more common are:

MARGINS

There is an astounding number of terms used to describe the margin of a leaf (or any other structure.) Some of the more common are:

CLIMBING PLANTS

Plants can climb by one of several methods:

ARMATURE

Plants can be armed in various ways:

TEXTURE

Succulent--swollen and juicy.  Eg., cactus stems and leaves of some plants.  Here is an extreme example of succulent leaves.
Coriaceous--stiff and leathery
Herbaceous--thin and leaf-like.  (May be applied to many different sorts of parts, such as sepals, etc.)
Membranous--thin and flexible, like a membrane. (In this photo, the bracts below the flowers)
Scarious--stiff, dry, and somewhat transparent or scaly, often yellowish, whitish, or brownish in color rather than green

PLANT HAIRS and TERMS TO DESCRIBE SURFACES

Plants can be glabrous (without hairs) or may have various sorts of hairs.  There are many terms used to describe the hairs or the surface.  Here are a few.
Simple hairs-- straight and unbranched
Stellate hairs--shaped like stars.  The rays may be free or fused
Glandular hairs--topped with a gland or swollen and gland-like.  You may also see stalked glands--glands with stalks stiffer than hairs
Branched hairs--the main hair has side branches (look at the hairs on the midrib of the leaf)
Plumose hair or bristle--the main hair has side hairs (the smaller side hairs are just visible on each big hair)
Scale--a thin, flat structure (like a fish scale), often attached in the center
Glaucous--glabrous and with a coating of wax
Ciliate--with short hairs around the margin
Pilose--with long, soft, spreading hairs.  Here is another example.
Pubescent--with short, soft hairs  (This term is sometimes incorrectly used to refer to having hairs of any sort)
Hispid--with stiff, spreading hairs.  Here is another example (look at the hairs along the veins)
Strigose--with rather stiff, appressed hairs
Scabrous--rough or sandpapery, with very short, stiff hairs or projections (Examine the close up shots of the leaves and stem)
Tomentose--with a dense, soft coat of hairs that is hard to see through, e.g., underside of mustang grape leaves
Arachnose--with long, tangled, cobweb-like hairs
Gland-dotted-- covered with scattered glands. These usually look greasy, or like little drops of yellow or dark oil.  Glandular punctate--with the scattered glands in the bottoms of little pits. (Look at the surface of the whitish bracts below the flowers)

CLICK HERE FOR THE PICK-TEN QUIZ OVER VEGETATIVE MORPHOLOGY

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last updated  25 June,  2010  by MDR