plant life cycles
There are two types of plant life cycles- those with a dominant sporophyte generation and those with a dominant gametophyte generation. The former type of plant has a seed but no fruit, while the latter type of plant produces both seeds and fruits.
Sporophytes are the diploid (2n) phase in the plant life cycle. The sporophyte phase produces spores by meiosis inside spore-bearing structures called sporangia. The sporophyte phase is free-living and independent; it typically dies soon after it produces spores. Most plant species on Earth today, including all known vascular plants (plants with xylem tissue), are sporophytes.
All plants have a life cycle that includes a seed stage. A few plants, such as ferns, mosses, and liverworts, have a dominant sporophyte generation and a seed but no fruit. These plants are said to produce naked seeds because the seeds are not protected by an ovary or other protective structure. Most other plants, however, produce seeds that are protected by a fruit. The fruit may be fleshy, as in tomatoes and bananas, or dry, as in beans and corn.
A fruit is a mature ovary of a seed plant. The term “fruit” is often used to refer to the edible component of a plant that contains seeds, such as tomatoes, potatoes, and wheat. However, not all fruits are edible. Some fruits are used for other purposes, such as for ornamentation (e.g. flowers) or for producing fibers (e.g. cotton).
The plant life cycle begins with the germination of a seed. The seed grows into a young plant (the sporophyte generation), which produces flowers (the gametophyte generation). Fertilization of the female gametes by the male gametes results in the production of seeds. The young plant that grows from a seed matures and produces its own seeds, and the cycle begins anew.
which plants have a dominant sporophyte generation?
Many plants have a dominant sporophyte generation, which means that they produce more spores than fertilized eggs. This is because the spores are less likely to be eaten by predators or to die from disease. Some plants, such as ferns, have a dominant sporophyte generation but no seed. Others, such as mosses, have a seed but no fruit.
Seed plants include both the gymnosperms, such as conifers, and the angiosperms, such as flowering plants. These two groups of plants are distinguished by how their seeds are produced and protected. All seed plants have a dominant sporophyte generation—that is, the plant that you see is mostly made up of the haploid spores that give rise to the next generation. Seed plants also produce a seed, which encloses and protects the embryo plant until it can grow into an independent sporophyte. In contrast, non-seed plants (such as mosses and ferns) have a dominant gametophyte generation—that is, the plant that you see is mostly made up of the diploid cells that give rise to gametes (sex cells). These gametes fuse to form embryos that grow into new sporophytes. Non-seed plants do not produce a seed; instead, they produce spores that give rise to new gametophytes.
All mosses have a dominant sporophyte generation and a seed but no fruit. This distinguishes them from both liverworts and hornworts, which have dominant gametophyte generations and no seed.
which plants have a seed but no fruit?
The seed is the main propagative unit in the plant kingdom. Many plants however, do not produce seeds but they do produce other means of reproduction. These plants still have a sporophyte generation, but they do not produce fruit. So, which plants have a seed but no fruit?
Gymnosperms are a group of seed-producing plants that includes conifers, cycads, ginkgo, and gnetophytes. The term “gymnosperm” comes from the Greek word gymnospermos, which means “naked seeds.” These plants produce seeds that are not enclosed in an ovary or fruit, as is the case with angiosperms.
Ferns are a type of plant that have a dominant sporophyte generation and a seed but no fruit. The spores of ferns are produced in specialised cells or structures called sporangia. When these spores mature, they are released and travel to new locations, where they germinate and grow into new plants.