The journey of pollen to a plant in photos

Link copiedShareShare article Drosera aberrans is native to New South Wales, South Australia, and Victoria.(Supplied: Yennifer Longo)Have you ever looked at a flower up close? Many of us know that for seeds to be made, pollen "lands on a flower" but what happens next? Welcome to the secret sex life of plants captured in images by botanists from around Australia. There are some key differences between plants and animals in the quest to reproduce. But plants are also a lot more like us than you might realise in some aspects of their anatomy and matchmaking strategies. Vibrant-coloured flower petals captivate us, but more importantly they are the first step in the journey to a seed for many plants. Not all plants use colour to attract insects and birds; some plants like grass don't rely on pollinators at all. But hidden within the petals of all flowers are the parts that really matter. Most plants have both male and female sex organs. The four "baubles" on the white and purple stalks are the male parts — the anthers — of the flower below. The female part is more cryptic than the showy yellow anthers of the male — just visible as two green spikes in this flower. The anthers contain pollen, which is not sperm but rather a container for plant sperm. When it is mature, the anther opens and releases the pollen. Anthers can open in many ways. Some, like the ones in purple in the next image, split vertically releasing pollen easily. Some anthers open from pores or slits at the top. Many plants with these types of anthers, such as the Guinea flower, rely on vibration from native bees to release the pollen. Each anther can hold thousands or millions of pollen grains depending on the species. But if flowers have both male and female parts, how do they ensure they don't mate with themselves? To make sure the seed is healthy, plants spread their pollen as far away as possible via the wind, water or by pollinators. Pollen comes in special shapes to help it spread. Spiky or irregularly shaped pollen is adapted to stick to the pollinators' bodies (or into our nasal passage). Round pollen has low wind resistance and will float long distances in the breeze, and is a feature of many grasses. Plants may also have special tricks to help pollen spread. Orchids, for example, deliver all their pollen in one sticky packet that adheres to the back of specialist pollinators that only visit flowers of the same plant species. Some plants go as far as trapping pollinators to ensure enough pollen has been deposited on their bodies before they are released. This also reduces the chances of self-pollination. The anatomy of sex organs in plants is similar to ours. Once the sperm-containing pollen lands on the top (stigma) of the female part, it travels down a tube (style) to reach the ovaries at the base — but only if the timing is right. Plants can time their fertility to prevent mating with themselves. The female stigma is only receptive at certain times and when this happens she produces a moist sugary secretion that helps pollen grains germinate. Pollen is the fastest growing plant cell. Once it lands on the receptive stigma pollen grows a tube, sort of like an erection. The pollen tubes, seen in the next image as fluorescent lines coming out of the kidney- shaped pollen grains, grow all the way down the long style of the female until they reach and fertilise the egg or ovule. Unlike animals, plants have two sperm. One sperm fertilises the egg to create an embryo — the solid white part at the centre of a seed. The other sperm helps to grow the paler coloured fleshy white mass surrounding the seed called the endosperm. The endosperm gives the seed energy to grow. It's also the part that gives us energy when we eat crops like wheat and corn. One pollen grain is needed to create one seed. This means many pollen grains are needed to fertilise plants with many seeds like those found in pea pods or corn cobs. A pod or a fruit is the dry and swollen part of the female plant. As the seeds — and the embryos within them —mature, the fruit ripens. A fruit can attract animals to disperse the seeds, or in the case of a pea pod, disperse seeds itself. Some seeds even have special modifications called arils to attract ants, which then carry them underground. When seed matures it will germinate and grow into a seedling. But unlike most animals, plants aren't on a timeline to grow up. Many plants can wait many years or even decades for the right conditions before a seed will germinate. Then it may be years, or even decades before they flower. But once they do, the process starts all over again. Hear more about the wonderful world of plants and pollination from Dr Chantelle Doyle on the Science Show. Lead image: (Drosera aberrans) Yennifer Longo Thanks also to: Natalie Allen, Tobias Hayashi, Susan Hoebee, Peter Lockhardt, Inna Osmolovsky, Ruby Paroissien, Carol Yan Copy linkFacebookX (formerly Twitter)Related topicsAust

The journey of pollen to a plant in photos

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