Describe the structure and state the functions of roots.

State the primary functions of the root - anchorage, water and mineral uptake.

ROOT

Anchorage – holds the plant in the ground. Water and mineral uptake.

Monocots only have a fibrous root system (adventitious arising from nodes on the stem), they do not branch or produce secondary thickening. Dicots have a tap root system (developing from the radicle) they branch and produce secondary thickening.

ROOT UPTAKE

Describe root types - ‘tap’, ‘lateral’, ‘fibrous’ and ‘adventitious’, to include the origin of each type e.g. tap root from radicle, adventitious roots from stem.

TAP ROOT Primary root – first root, origin from the radicle (tap root of tree/or biennial, e.g., carrot).

LATERAL ROOT Secondary/lateral – roots coming off the primary root producing the mass of the root system for anchorage, water absorption and mineral uptake.

FIBROUS ROOT The root system of monocotyledonous plant arising from the central apex of the plant. Straight growing, not normally able to branch.

ADVENTITIOUS ROOT Roots coming off any other part of the plant other than the primary root system. Origin – off stems/stolen/aerial/from cuttings. Some plants produce adventitious roots off their stems which cling onto rough surfaces, allowing the plant to grow up the surface as a climbing plant, e.g., Hedera helix.

RADICLE First part to emerge from the seed, forming the main root. embryonic root

Describe the difference between monocotyledon and dicotyledon roots.

MONOCOT ROOT

DICOT ROOT

Describe the structure of the root and state the function of its components - internal and external structures to include drawings of transverse and longitudinal sections through a young dicotyledon root to show the following components: root cap, apical meristem, zone of elongation, zone of differentiation, root hairs, epidermis, cortex, endodermis, pericycle, phloem, xylem and cambium.

ROOT GROWTH

ROOT CAP

Protection and lubricates the root. May inhibit the roots of other plants. Influences ion uptake. Attracts beneficial soil micro-organisms. Glues soil particles to the root so improving the soil/plant contact. Protects the root cells from drying out. Physically protects the root meristem.

ROOT HAIR Root hairs – produce a vast surface area for water and mineral uptake.

CORTEX See Root Cortex & STEM CORTEX

ROOT CORTEX Packing and connective cells. Stores starch and produces energy (respiration).

ENDODERMIS Protection of inner vascular bundle. Controls water and mineral uptake.

PERICYCLE Gives rise to lateral roots.

Describe how the root is adapted to perform other functions - storage/perennation, tap root (Daucus) and root tuber (Dahlia), climbing (Hedera) and support/prop (Zea).

PERENNATION Tap root stores food, mostly as sugars and takes the plant over the winter. In spring the plant produces a flowering shoot, Daucus carota subsp. sativus.

PERENNATING ORGAN

TUBER Root tuber plant stores food in swollen root tubers, e.g., Dahlia variabilis. Plant regrows from buds on the base of the stem. Tubers have no buds.

ROOT ANCHORAGE Prop roots – some plants produce adventitious roots off their stems which grow down into the soil so supporting tall plant, e.g., Zea mays.