Question

Explain how a sporophyte in a hornwort is a nutritionally dependent organism?

Answer 1

The sporophyte is a diploid and multicellular stage in the life cycle of a plant like a hornwort or an alga. When an egg cell that is haploid is fertilized by a sperm that is also a haploid cell a zygote is formed that develops into the diploid sporophyte. Therefore this sporophyte has two sets of chromosomes that come from both the parents.

Hornworts are included as a group in non-vascular plants of division Anthocerotophyta. The common name “hornwort” refers to a horn like an elongated structure that is the sporophyte of the plant. They usually grow on rocks and damp soil in tropical and regions of warm temperature. They have ancient lineages and are the earliest plants to evolve on land. The sporophyte is dependent for its nutrition and water on the attached gametophyte. Gametophyte phase is a flattened and green photosynthetic plant body of hornwort. This ecologically persistent and photosynthetic stage of the life cycle is the haploid and gametophytic generation. The diploid sporophyte is attached to gametophytes and depends on them for their nutrition as they themselves are not photosynthetic. They only contain an unbranched stalk or seta and a single terminal sporangium.

A sporophyte develops from an egg that is held in a flask like “archegonium”. It is fertilized and grows further by forming additional cells. The embryonic sporophyte becomes elongated and one of its portions becomes a foot penetrating the gametophyte and anchoring the sporophyte to the gametophytic body. On the other end, spore-bearing “capsule” develops along with supporting stalk (also called seta ).