Xerophytes Flashcards
what are the strucutral adaptations of xerophytes
- thick, waxy cuticle
- small leaf surface area
- sunken stomata, rolled leaves with stomata on the inside
- well established root systems
what are the physiological adaptations of xerophytes
- stomata opening at night (reverse stomatal rhythm)
- storage of water in succulent tissues
how does a thick waxy cuticle work and give an example
impermeable to water, preventing evaporation and water loss. stops uncontrolled evaporation through leaf cells. e.g. australian succulent Sturts Pigface
how does a small leaf surface area work and give an example
fewer stomata, leading to reduced water loss. less surface area for evaporation. smaller surface area of lead is exposed to the drying effects of the wind, reducing evaporation and reducing water loss. e.g. conifer needles, cactus spines.
how does a sunken stomata, rolled leaves with stomata on the inside work and give an example
stomata in sunken pits within rolled leaves prevent water loss by increasing the relative humidity in the vicinity of each stoma, decreasing the concentration gradient and reducing evaporation and diffusion. creates a micro-climate. e.g. Porcupine Grass
how does a stomata opening at night work and give an example
this assists in reducing water loss because the stomata are closed during the hottest part of the day, reducing water loss by transportation/evaporation (CO2 uptake occurs at night and it is then stored for use in photosynthesis during the day). e.g. Porcupine Grass. The cooler temperatures allow the plant to take up CO2 through their stomata without sacrificing water.
how does storage of water in succulent tissues work and give an example.
Plants store water in cells in fleshy stems of leaves instead of transpiring it out of plant, for use during dry periods; reduced water loss during hot dry periods. e.g. Gunniopsis Quadrifida
how do well-established root systems aid in water retention
Grow deeply and in all directions in order to anchor the plants in sandy soil and against the wind.
Helps to maximize water uptake.
what are the physiological features to discuss with halophytes and xerophytes ?
- rate of transpiration
- gas exchange
- absorption of water
morphological features of the leaves of xerophytes
Leaves may be thin or rigid, fleshy and leathery.
morphological features of the stems of xerophytes
Stem is aerial, mostly erected but with limited growth.
The stem is rigid and stout.
morphological features of the roots of xerophytes
Large elaborate root system occurs. Roots are mostly tap roots penetrating great depth of soil.
rate of transpiration in xerophytes
Rate of transpiration is decreased or entirely checked by heavy cutinisation of epidermis and by the formation of sunken stomata.
gas exchange in xerophytes
Gases exchange of both aerial and underground plant parts with the atmosphere takes place normally.
absorption of water in xerophytes
Absorption of water and mineral salts takes place by the help of long-seated root system.
The root systems of xerophytes often include spreading roots just beneath the soil surface.
Outline two advantages of these surface roots for xerophytes.
Xerophytes are plants that live in arid regions, that is, regions that experience very high temperatures and receive little rainfall. Because of this, xerophytes require adaptations that allow them to access, store and utlise water efficiently in order to survive. Two advantages of spreading roots just beneath the soil surface for xerophytes are:
Large surface area of roots
Roots cover a large surface area
Increases chances of finding water, provide anchorage and more room to store water
Roots close to the soil surface
Can access surface water or small amounts of water on the surface
Can absorb water before it evaporates or can quickly absorb water
Explain the problems that a plant experiences in obtaining water from soil with a high-salt content.
When a plant obtains water from soil with a high-salt content, salt concentration in the soil exceeds that in the roots. This causes water to move from the roots into the soil by osmosis. This movement occurs in order to equal the concentrations of salt inside and outside the root. This is problematic as the plant loses water and becomes dehydrated. The plant needs to then reverse this process in order to obtain water, which requires valuable energy.
