Which of the following is NOT listed as a possible external agent for pollination?

Fungi

The correct answer is Option (4)- Fungi.

The plants use two abiotic (non-living) agents and one biotic (living) agent for pollination. The abiotic agents are wind and water, while the biotic agent mentioned is animals. Fungi are not listed as a possible external agent for pollination.

Wind pollination, also known as anemophily, occurs when pollen grains are carried by the wind from the anthers of one flower to the stigma of another flower. This type of pollination is common in plants with small, light pollen grains that are easily carried by air currents. Examples of wind-pollinated plants include grasses, many trees (such as conifers), and some cereal crops.

Water pollination, or hydrophily, Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons. Some examples of water-pollinated plants are Vallisneria and Hydrilla which grow in fresh water and several marine sea-grasses such as Zostera. Water-pollinated flowers are not very colourful and do not produce nectar.

Insect pollination, or entomophily, involves the transfer of pollen grains by insects such as bees, butterflies. Flowers that rely on insect pollinators often have bright colors, attractive scents, and nectar rewards to attract the insects. The insects inadvertently pick up pollen on their bodies as they move from flower to flower, and when they visit another flower of the same plant species, the pollen can be transferred to the stigma.

Fungi, on the other hand, are not typically involved in the process of pollination. They are more commonly associated with decomposition, nutrient cycling, and symbiotic relationships with plants (such as mycorrhizal associations). While fungi may play important roles in the ecosystem, they are not recognized as external agents for pollination in the context of flowering plants.