Herbaceous Stems

The Stem

This organ is responsible for the aboveground structure of the plant, and is involved in both structural support and vascular transport.Recall the general external anatomy of a stem:

Recall the locations of the apical and lateral meristems.

  • APICAL meristems (located at the tips of roots and shoots) give rise to three PRIMARY MERISTEMS (protoderm, ground meristem, and procambium).

And also recall:

  • ground meristem - develops into ground tissues
  • procambium - develops into vascular tissues and the vascular cambium
  • protoderm - develops into the dermal system

A cross section of a generalized, herbaceous dicot stem appears on the left:

Note that young, herbaceous stems may have stomates for gas exchange, though the leaf is the main site of gas exchange, with many more stomates than the stem.

Secondary Growth in Stems

LATERAL MERSTEMS are cylindrical, secondary meristems in both stem and root that give rise to either vascular tissue or secondary dermal tissues. They are the
  • vascular cambium - located between xylem and phloem
  • cork cambium - located between phloem and bark

Recall the progression of secondary growth in the two lateral meristems.

  • determinate growth: growth that occurs during a finite juvenile phase, and then stops.
  • indeterminate growth: growth that occurs throughout the life of the organism.
  • annual plant: lives for about a year, flowers and dies
  • perennial plant: lives for more than one year

Annual plants lack secondary growth, and remain herbaceous throughout their short lives. Many perennials do not develop true wood, though they may become somewhat "woody" as their older tissues lignify and become more structurally supported with cellulose, resins, and other substances.

Still others may undergo extensive tissue growth via the vascular cambium. Only these plants produce what is known as true, botanical WOOD.

Stems and Wood

All plants begin their development as HERBACEOUS (i.e., non-woody) organisms. True WOODY plants eventually develop WOODY stems.

Shown diagramatically, the tissue layers are arranged like so:

  • heartwood: dead center of the woody stem in which conducting elements of xylem are clogged with tannins and resin, and no longer function to conduct fluids.
  • sapwood: external ring of xylem still conducting fluids
  • springwood: large-lumen xylem formed in spring
  • summerwood: small-lumen xylem formed in summer/late autumn, just before dormancy

The wood of many species may contain species-specific aromatic compounds. Consider:

  • Why put those in the wood, of all places?
  • What side effects might this have on humans who use wood?
  • wood turning
  • wood shavings used for litters
  • aromatic wood insect repellants

Monocot Stems

No tour of stems would be complete without a brief mention of the highly derived stems of monocot anthophytes. A cross section is shown on the right of the diagram we saw above:

Note the absence of concentric rings of vascular tissue. Instead, xylem and phloem are both distributed throughout the pith of the stem in discrete vascular bundles.

Many phases of propagation

2009-07-01 10:34:10 by AnitaMoPlants

You were correct in eliminating some of the leaf surface and making a shallow wound in the base of the stem.
For soft wood stem cuttings one usually makes a clean cut just below a node in the stem and then a one inch sliced wound .
You may not have lost the plant. Roots may form this autumn.
The leaves may have fallen from drying out or perhaps a fungus formed in the soil
With evergreen leaf cuttings I sometimes will put plastic over the cuttings to keep the humidity up .
Environmental control such as stress, too much water, not enough light or a soil fungus appearance are all plausible reasons for the leaf drop

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DALY: Use care when planting around septic drainfields  — Gwinnettdailypost.com
Shallow rooted annual and perennial herbaceous plants can be planted closer to the drain fields since they do not have invasive roots. Turfgrass can be grown over the drain field and is beneficial since it helps hold the soil in place.

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