3.6 Xerophytic adaptations

Question 1

Xerophytic Adaptations.

Morphological Adaptations - Roots

Answer 1

Most have large well developed root system.
Perennial xerophyte penetrate deeper into soil, for water absorption.
When water is present on soil horizons at surface roots may be shallow.

Question 2

Xerophytic adaptation.
Morphological adaptations.
Stems

Answer 2

Dense woody stems.
Modification of stems into thorns eg. Duranta
Possible covering of hair (pubescence) eg. Calotropis
Possible covering of layer if wax eg.Equisetum
Possible modification for storing water eg.
i PHYLLOCLADES - modified stem/shoots, looks like leaves eg. Opuntia.
ii CLADODES - limited growth, single or two internodes eg. Asparagus app.

Question 3

Xerophytic adaptations.
Morphological adaptations.
Leaves.

Answer 3

Microphyllous - small scaly leaves eg. Casuarina or needles eg. Pinus.
Rolled foliage with inward facing stomata eg. Ammoohila.
Trichophyllous - leaves covered in hairs (pubescence) eg, Nerium or Calotropis.
Sclerophyllous - rigid, stiff foliage eg. Banksia.
Macrophyllous - sort, fleshy leaves. Begonia.
Foliage may absciss early eg. Euphorbia this is known as caduceus.
In many cases foliage maybe absent in xerophytic plants eg.
Capparis

Question 4

Xerophytic adaptations.

Anatomical adaptations- Epidermis and Hypodermis.

Answer 4

Epidermis.
May have multiple layers eg. Nerium.
Epidermal cuticle will be thickened with wax or resin deposits.
Hairs present in grooved furrows - protect the stomata which will be sunken in the grooves.
Stomata can be sunken in pits in foliage.
Numbers if stomata in foliage is often small.
Foliage capable of rolling have special bulliform cells which assist in leaf rolling.
HYPODERMIS may be thickened for protective function maybe adapted for water storage.

Question 5

Xerophytic adaptations.

Ground tissue and conducting tissue.

Answer 5

Hypodermis tissue in xerophytes are in layers which are thickened and well developed, they are referred to as ground tissue.
Eg. Succulents have cortex charged with water or types of mucilage eg. Latex.
Intercellular spaces are smaller.
Stems may be able to photosynthesise to compensate for smaller leaves.
Stems have mechanical support tissues eg. Casuarina spp.

Question 6

Xeromorphis example:
Pinus
Part 1

Answer 6

Mesophyll cells are modified with resin canals embedded in them, protect against pests and diseases.
Pine needle has a small surface area.
Thicker waxy cuticle layer.
Sunken position of stomata on surface.

Question 7

Xeromorphic adaptations.
Pinus
Part 2

Answer 7

Sunken stomata
Thick cuticle and presence of Hypodermis to reduce water loss.
Transfusion tissue surrounds vascular bundle. This tissue seems to hep transport materials in and out of vascular tissue.
Resin ducts carry resin,a hydro carbon, contains substance that may help protect leaves.
Pine phloem lacks companion cells, albuminous cells perform similar function for phloem.