PLANTS – DAY 3

MONOCOT & DICOTS

INTRODUCTION

There are different classes of plants – one of these classes of plants are called angiosperms, and these plants produce flowers.

Angiosperms can be further divided into 2 subclasses: Monocotyledoneae and the Dicotyledoneae, aka monocots and dicots

Names of 2 subgroups are based on structure of their seeds

SEEDS

The seed, which surrounds the plant embryo and protects it from desiccation in the uncertain conditions of a terrestrial environment, is one of the adaptations that has allowed plants to thrive as they gradually moved from water to land.

Each seed consists of an embryo, food source, and protective outer coat; it can lie dormant for some time before germinating, waiting until environmental conditions are right

Monocots have only 1 seed leaf, cotyledon Dicots have two cotyledon or seed leaves Cotyledons store nutrients/carbohydrates that

nourish the embryo of the plant as it develops. Cotyledons are often the first leaf to appear as the seed germinates

MONOCOT & DICOT SEEDS

EXAMPLES OF MONCOTS & DICOTS:

MONOCOTS:Onion, corn, rice,

sugarcane

DICOTS: tomatoes, cabbage, apples, peaches

SUMMARY OF DIFFERENCES:

DICOTS

MONOCOTS

TISSUE TERMS

Vascular cambium/cylinder: meristematic tissue responsible for creating new xylem and phloem tissue

Pith: the parenchyma tissue at the very center of roots AND stems. Functions in storage of nutrients, carbohydrates and water

Cortex: parenchyma tissue surrounding the pith; made of rigid cells in roots AND stems

Pericycle: a thin layer of lateral meristematic cells that surrounds the vascular cylinder; helps for secondary roots to grow

Endodermis: layer of rectangular cells surrounding the vascular cylinder; innermost layer of the cortex; regulates movement of water and minerals

Epidermis: the outermost layer of a multicellular plant experiencing growth

Vascular Bundles: collections of xylem and phloem tissue, separate from other collections of cells, running longitudinally - includes xylem and phloem

ROOT TISSUE DIFFERENCES

Xylem in center of root in an ‘X’ shape; phloem is outside of xylem Vascular

bundles are arranged in a ring shape

MONOCOT ROOT CROSS SECTION

DICOT ROOT CROSS SECTION

CORTEX

EPIDERMIS

STEMS – MONOCOT & DICOT

DICOT STEM CROSS SECTION

In herbaceous dicots, bundles are arranged in a ring

A thin layer of tissue called vascular cambium between xylem and phloem – can appear as a hollow area in the plant (buttercup)

MONOCOT STEM CROSS SECTION

MONOCOT STEM VASCULAR BUNDLE

Herbaceous monocots have vascular bundles scattered throughout the stem (corn)