Modes of reproduction in plants

Did you know that plant reproductive diversity is as wide as its ecosystems, growth forms, and colors?

The process by which plants produce new children, or ‘offspring’ is called ‘reproduction’. All living organisms reproduce to ensure the continued existence of the species.

You may have heard or read about how flowering plants reproduce. But, what about plants without flowers? They can reproduce sexually and asexually too. Believe it or not, asexual reproduction in plants is much more common.

The plant kingdom is full of surprises and that is why we want to talk briefly today about the different modes of reproduction. Let us start by understanding sexual reproduction.

Sexual reproduction

The core of sexual reproduction is the genetic material ‘DNA’ from both parents. The DNA comes from plants sex cells called ‘gametes’. By ‘fertilization’ the genetic material from two sex cells combines and produces offspring. The information contained in the genetic material can help the offspring to adapt to environmental changes among generations. Flowering and non-flowering plants can reproduce sexually.

How do plants with flowers reproduce sexually?

Flowering plants are known as ‘angiosperms’.Angiosperms have stems, roots, and leaves. They produce seeds and have male and female organs within the flowers. Those plants reproduce by ‘pollination’.

Pollination is the process by which pollen is taken from ‘anthers’ (part of male sex organs, where the pollen is made) to the ‘stigma’ (female part of the flower). The pollen is carried by wind or insects to fertilize the egg and forms the seed.

Plants can either ‘self-pollinate’ or ‘cross-pollinate’:

• Self-pollination occurs when the pollen of a plant fertilizes its own egg. Very common in ‘hermaphrodite’ plants which carry both female and male sex in the same flower.
• Cross-pollination happens when the pollen travels from anthers to the stigma of a flower from a different plant.

How do plants without flowers reproduce sexually?

Non-flowering plants can reproduce by spores or seeds.

Plants like mosses, liverworts, and hornworts, known as ‘Bryophytes’, reproduce by spores. Bryophytes are nonvascular plants, which means they also lack roots, stems, and leaves. Bryophytes male gametes (the sperm) are carried by water to the female gametes (the eggs). When the sperm fertilizes the egg, the spore capsules are produced.

Ferns, so-called vascular plants (they have roots, stems, and leaves, but not flowers), also reproduce by spores.  

Conifers, also known as ‘Gymnosperms’, reproduce by seeds. However, they do not have flowers. coniferous plants reproduce by growing seeds inside of cones. These cones ripen over the course of weeks, and the seeds are then dispersed.

Asexual reproduction

As we mentioned before, asexual reproduction is conventional in plants. By asexually reproduction plants can reproduce, but the offspring are identical to the parent plant mainly because there is no fusion of male and female gametes. Genetically identical offspring are called ‘clones’. Clones lack genetic diversity. This makes them more susceptible to diseases. It also makes them less adaptable to changes in the environment.

There are a few methods of asexual reproduction. They include vegetative propagation and fragmentation.

Vegetative reproduction

Vegetative propagation does not need seeds or spores. Instead, offspring grow directly from the parent plant. Vegetative propagation varies among species. Here are a few forms of vegetative reproduction in plants:

• Bulbs: Those are underground buds that have fleshy leaves extending from them. Bulbs are food storage units for future developing plants. These new buds can eventually develop into new plants. Garlic, onions, daffodils, and tulip plants all reproduce using true bulbs.
• Corms: These are similar to bulbs, but do not have as many layers. They grow in similar size and can remain dormant in adverse conditions. Corms can be cut into pieces and each piece planted to produce a new plant. Banana and agave (Tequila plants) reproduce by corms.
• Tubers: As modified stems, most tubers bear minute scale leaves, each with a bud that has the potential for developing into a new plant. Potatoes and taro reproduce using tubers.
• Rhizomes: Rhizomes are subterranean stems with roots, they branch and produce new shoots. Ginger and bamboo are examples of rhizomes. 
• Stolons: Look like branches growing on the ground which develop roots and grow into new plants. Strawberry and mint are good examples.

An advantage of asexual reproduction is that the resulting plant will reach maturity faster. Since the new plant is arising from an adult plant or plant parts, it will also be sturdier than a seedling.

Apomixis – seed without fertilization

Apomixis refers to the formation of seeds without fertilization. The offspring is a clone of the female parent plant. Plants of more than 35 families are known to be apomictic which also include cereals such as, maize and wheat. Apomixis is the most cost-effective method to produce seeds and prevents losses of specific characters of the hybrid.

A deep understanding of reproduction and pollination of different species is crucial for breeding. The science of reproduction provides a solid foundation for selecting the best breeding techniques for plant genetic development.

We hope you enjoyed the ride through plant reproduction today.

Keep an eye on this space for more!

By Nataly Sánchez Del Río | 7 June 2022

References:

• Amasino, R. M., Cheung, A. Y., Dresselhaus, T., & Kuhlemeier, C. (2017). Focus on Flowering and Reproduction. Plant physiology, 173(1), 1–4. https://doi.org/10.1104/pp.16.01867
• Barrett S. C. (2010). Understanding plant reproductive diversity. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 365(1537), 99–109. https://doi.org/10.1098/rstb.2009.0199
• Asker, S.E., & Jerling, L. (1992). Apomixis in Plants (1st ed.). Routledge. https://doi.org/10.1201/9781315137537
• Barcaccia, G., & Albertini, E. (2013). Apomixis in plant reproduction: a novel perspective on an old dilemma. Plant reproduction, 26(3), 159–179. https://doi.org/10.1007/s00497-013-0222-y
• Orton, T. J. (2019). Breeding Methods for Outcrossing Plant Species: III. Asexual Propagation. Horticultural Plant Breeding, 309–326. https://doi.org/10.1016/B978-0-12-815396-3.00017-2
• Priyadarshan, P. M. (2019). PLANT BREEDING: Classical to Modern. https://doi.org/10.1007/978-981-13-7095-3