Plant Morphology: Roots and Root Systems

Plant Morphology

• Plant morphology or phytomorphology refers to the study of the physical form and external structure of plants

Roots and its Structures

• Roots are the underground parts of a plant responsible for absorbing water and nutrients, anchoring the plant in the soil, and sometimes storing food
• Geotropic roots exhibit growth in response to gravity
• Phototropic roots exhibit growth in response to light
• Hydrotropic roots exhibit growth in response to water
• Primary roots/radicle represents the first root emerging from a germinating seed
• Secondary roots arise from the radicle
• Tertiary roots originate from the secondary roots

Types of Root Systems

• Tap roots are prominent in dicots
• Fibrous roots are prominent in monocots
• Adventitious roots develop from organs of the shoot system
• Tap roots grow & become stout
• Roots develop from lower nodes
• Adventitious roots develop from organs of the shoot system
• Secondary & tertiary roots grow from the primary root
• Fibrous roots have the same length & diameter

Stem and its Structures

• The stem supports leaves, flowers, and facilitates the transport of water and nutrients
• A node represents the point on the stem where leaves, branches, or flowers grow
• An internode signifies the region between two nodes
• Buds are growth points that develop into new shoots, leaves, or flowers
• Underground stems grow below the soil and store food
• Aerial stems grow above the ground, supporting leaves, flowers, and fruits
• Sub-aerial stems grow partly above and partly below the ground, aiding in vegetative reproduction

Flower and its Structure

• A flower constitutes the reproductive part of a plant that produces seeds, often leveraging colorful petals to attract pollinators
• A flower is composed of four essential components: petals, sepals, stamen, and pistil
• Petals are colorful structures designed to attract pollinators
• Sepals are green leaf-like structures safeguarding the flower bud
• The stamen (male part) includes the anther, which produces pollen, and the filament, which supports the anther
• The pistil (female part) consists of the stigma, a sticky part for capturing pollen, the style, a tube connecting the stigma to the ovary, and the ovary, which houses ovules that develop into seeds following fertilization
• Monocots typically have floral parts in multiples of three
• Dicots usually display floral parts in multiples of four or five

Leaf and its Structure

• A leaf is a flat, green plant organ facilitating food production via photosynthesis and participating in gas exchange and water regulation

• A leaf encompasses three primary components: the blade (lamina), the petiole, and the leaf base

• The blade (lamina) represents the flat, green part responsible for absorbing sunlight during photosynthesis

• The petiole serves as the stalk connecting the leaf to the stem

• The leaf base is the area where the leaf attaches to the stem, sometimes with small structures called stipules

• Other structures of the leaf include:

• The midrib, which constitutes the central vein providing support

• Veins, which are responsible for transporting water, nutrients, and food

• Stomata, which are tiny openings crucial for gas exchange

• A simple leaf has one whole blade attached to the stem by a single stalk (petiole)

• A compound leaf is comprised of multiple leaflets connected to a single main stalk (petiole)

• The lamina/leaf blade functions as the flat, broad part of the leaf that captures sunlight for photosynthesis

• The apex/tip is the tip of a leaf, which varies in shape

• The leaf base represents the lowest section of a leaf, establishing the connection point to either the stem or the petiole

• The petiole serves as the stalk that links the leaf blade (lamina) to the stem of a plant

• Stipules are diminutive, leaf-like structures situated at the base of a leaf stalk (petiole), serving to safeguard developing leaves and may fall off as the leaf matures