SUPPORT IN AQUATIC PLANTS

SUBMERGED PLANTSHydrilla sp.

Curly-Leafed Pondweed

American Pondweed

• Thin, narrow and flexible leaves

• There are air sacs within the leaves and stems which keep the plants afloat close to the surface to obtain maximum sunlight• Water provides buoyancy (water buoyancy) which

support these plants

Provide little resistance to water flow

This means submerged plants can be tugged at and pulled by water currents with little damage

If these plants are removed from water, they become limp and floppy

FLOATING PLANTSWater Hyacinth

Bladderwort

Duckweed

Water Lettuce

• Broad leaves that are firm but flexible enough to resist being torn by wave action• Aerenchyma tissues in the stems and leaves

Spongy tissues with large air spaces between the cells

Provide buoyancy so that plants can float on the surface of the water

TERRESTRIAL PLANTSNON WOODY PLANTS WOODY PLANTS

NON-WOODY PLANTS• Herbaceous plantsi. Support is provided by turgidity of the parenchyma and

collenchyma cellsii. The thickening of the cell walls with cellulose and pectin in the

parenchyma cells provide additional mechanical strength.iii. Example:

Balsam Spinach Maize

• Climbersi. Have tendrils which grow from the base of leaf stalks. Ex: Morning glory

ii. Have thorns to hook on to a nearby support.Ex: Rose

2.3 SUPPORT SYSTEMS IN PLANTS

• COLLENCHYMA • SCHLERENCHYMA

SUPPORT IN WOODY PLANTS

• XYLEM

2.3 SUPPORT SYSTEMS IN PLANTS• Woody plants

– Support provided through tissue modification– Xylem tissue

• Consists of xylem vessel and tracheids• Strenghtened by lignin during development (primary

growth)• Lignin – tough, inelastic and not permeable to water• Store starch, sugars and water• It become turgid – give support• Lignin allows the formation of different types of

vessels (primary xylem, primary growth)• As plants grow, they undergo secondary growth and

form secondary xylem (wood)

2.3 SUPPORT SYSTEMS IN PLANTS• Woody plants

– Collenchyma tissues• Thickened with cellulose and pectin

– Schlerenchyma tissues• Thickened with lignin• Support non-growing parts of plants