Unit 2 Plant Anatomy Horticulture Stems Unit 2 Plant Anatomy Horticulture

Objectives Describe the purpose of the stem Label the parts of a stem and tell what they are for Identify various types of stem structures

Purpose Conduct water and minerals from the roots to other parts of the plant Conducts food made in the leaves to other parts of the plant Supports leaves and reproductive structures (fruit, flowers) Produces new leaves, flowers, and branches

Internal components of the stem There are 4 major internal components of the stem a. Xylem b. Phloem c. Cambium d. Pith

Vascular System composed of the xylem and phloem In monocots: bundles Xylem conducts water and minerals Phloem conducts food (carbohydrates/ Sucrose, amino acids, and hormones) In monocots: bundles In dicots, form rings inside the stem. (Phloem in near the bark and the xylem is the inner ring)

Cambium meristematic tissue (Growth tissue) located between the xylem and the phloem inside the stem responsible for the stems increase in diameter as it produces more xylem and phloem.

Pith stores food and moisture the center part of the stem (dicots)

Outer Parts of the Stem1 Nodes area of the stem where leaves are located areas of great cellular activity and growth where auxiliary buds develop into leaves or flowers

Internodes area between the nodes Length varies between internodes for different reasons: Time of season Health of the plant Early growth vs. later growth Speed of growth

Terminal Bud: a bud that contains cells of undeveloped leaf, stem, flower, or a mix of all. is positioned at t the tip of the stem sometimes forms the central leader or main trunk of the plant

Bud scale tiny leaf-like structures that cover the bud before it opens and grows. can have different shapes, sizes, and colors5.

Axillary or Lateral Bud a bud that will produce a new leaf or stem located along the side of the stem.

MODIFIED STEMS: Most stems are above ground; however there are certain stems that may be below ground. Above ground MS: crowns, stolons, spurs Below ground MS: bulbs, corms, rhizomes, and tubers

Spurs a compressed fruiting branch Short, stubby, side stems that arise from the main stem Common on fruit trees (pears, apples and cherries)

Stolons a horizontal stem that is fleshy or semi-woody and lies along the top of the ground Runner: a specialized stem that grows on the soil surface and forms a new plant at one or more nodes. EX. Strawberries and spider plants.

Tubers Enlarged portion of an underground stem like a potato that store food for the plant The eyes of the potato are the nodes on the stem Each eye contains a cluster of buds

Rhizomes: stem that grows horizontally at or just below the soil surface. storage organ and means of propagation some are compressed and fleshy: Iris some are slender with elongated

Bulbs shorten; compressed underground stems surrounded by fleshy scales Bud at top of scale many bulbs require a period of low-temperature exposure before they begin to send up the new plant

Corms shaped similar to bulbs, but do not contain fleshy scales. Buds and shoots arise from the crown and fibrous roots are fond on the bottom of the tuberous system.

Scale Runner