Plant Tissues (Leaving Cert Biology): Revision Notes

Plant Tissues

• Plants belong to the kingdom Plantae.
• They are multicellular organisms that make their own food (autotrophic).
• Flowering plants (angiosperms) are the most diverse members of the plant kingdom.
• Flowering plants are divided into two groups:
  • Monocotyledons (e.g., grasses, cereals)
  • Dicotyledons (e.g., dandelion, carrot, oak tree)

What is a Cotyledon?

• A cotyledon is an embryonic seed leaf that stores food.
• Why is this important?
  • Seeds planted underground cannot photosynthesize due to lack of sunlight. They use the stored food for growth.
• Once the seed germinates and true leaves develop, cotyledons are no longer needed.
• Monocots have one cotyledon in their seed (e.g., grasses, cereals).
• Dicots have two cotyledons in their seed (e.g., dandelion, carrot, oak tree).

Monocots vs Dicots

Monocots	Dicots
Seeds contain 1 cotyledon	Seeds contain 2 cotyledons
Mainly herbaceous (no woody parts)	Herbaceous or woody
Long narrow leaves	Broad leaves
Parallel leaf venations	Netted venation
Vascular bundles scattered at random in the stem	Vascular bundles form a ring in the stem
Flowering parts in multiples of 3	Flowering parts in multiples of 4 or 5
Fibrous root system	Tap root system
E.g., Daffodils, tulips, grasses	E.g., Beans, peas, oak, ash, elm, carrot

Plant Tissues

There are four main plant tissues:

1. Dermal tissue
2. Ground tissue
3. Vascular tissue
4. Meristematic tissue

1. Dermal Tissue

• Forms the outer protective layer of the plant.
• In the roots, dermal tissue is specialised to absorb water.
• In the leaves, it's specialised to secrete a waxy cuticle to prevent water loss.

2. Ground Tissue

• Makes up most of the plant.
• Functions vary depending on its location:
  • Photosynthesis in leaves.
  • Support in stems.
  • Storage in roots.

3. Vascular Tissue

• The plant's transport system. It is made up of:
  • Xylem: Transports water and dissolved minerals from the roots upwards.
  • Phloem: Transports food from where it is produced to where it is needed.

4. Meristematic Tissue

• Found in root and shoot tips and in all buds.
• Meristematic tissue (meristem) develops into each of the other 3 tissue types.
• Plants only grow at their tips. This happens at apical meristems.
• As a plant grows taller, its stems and roots thicken to provide extra support.