ADVANCED LEVEL: PLANT FUNCTIONS AND ADAPTATIONS

As we delve deeper into plant biology, we explore how plants adapt to their environments and the more complex mechanisms that enable them to thrive.

Adaptations for Water Conservation

Plants in dry environments (deserts) face water scarcity. Many of these plants, such as cacti, have adaptations to minimise water loss, including a thick cuticle, which is a waxy coating on the leaves that helps prevent water loss. CAM photosynthesis is another adaptation where plants open their stomata at night to minimise water loss, fixing CO₂ in the dark, then using it during the day to continue photosynthesis.

C4 Photosynthesis: A Special Adaptation

In hot and dry conditions, some plants use a modified form of photosynthesis known as C4 photosynthesis. In this process, carbon dioxide is first fixed into a four-carbon compound, which is then transported to specialised cells (bundle sheath cells) where the Calvin cycle occurs. This minimises water loss and maximises efficiency in environments with high temperatures and light intensity. Common C4 plants include maize and sugarcane.

Pollination and Seed Dispersal

Plants reproduce sexually through the formation of seeds, and pollination is key to this process. Pollination occurs when pollen is transferred from male to female reproductive structures, typically via wind or animal pollinators. Once pollinated, the seed develops and is dispersed in a variety of ways:

Wind dispersal – Seeds are carried by the wind (e.g., dandelions).
Animal dispersal – Seeds may attach to animals or be eaten and excreted.
Water dispersal – Seeds can float and be carried by water.

Secondary Growth and Woody Plants

Secondary growth occurs in lateral meristems, which produce secondary xylem (wood) and phloem. This process allows plants to increase in girth. As plants mature, woody plants like trees develop a hard outer layer of bark and gain the strength to support large structures.

Phytoremediation: Plants and Pollution

Some plants can absorb and detoxify pollutants from the environment, a process known as phytoremediation. For example, certain plants can absorb heavy metals from contaminated soil and store them in their tissues, reducing pollution.

Symbiosis with Fungi

Many plants, especially those in nutrient-poor soils, form mutualistic relationships with fungi. The mycorrhizal fungi attach to plant roots, extending them further into the soil to increase nutrient absorption, especially phosphorus. In exchange, the plant provides sugars produced by photosynthesis to the fungi.

ADVANCED LEVEL: PLANT FUNCTIONS AND ADAPTATIONS