Plants are living systems that carry out several essential processes. Through photosynthesis, they convert sunlight, carbon dioxide, and water into sugars and oxygen, fueling their growth. They then break those sugars back down through respiration to release the energy needed for development. Water moves through the plant and is released as vapor through the leaves in a process called transpiration, which helps cool the plant and pulls nutrients upward from the roots.
Reproduction in flowering plants centers on the flower, which contains four main parts: sepals that protect the developing bud, colorful petals that attract pollinators, stamens (the male parts) that produce pollen, and pistils (the female parts) that receive it. Pollination occurs when pollen transfers from the anther to the stigma, and common pollinators include bees, butterflies, moths, beetles, birds, and bats, with wind also serving as a pollinating force for many grasses and trees. Cross-pollination happens when pollen from one plant fertilizes another of the same species, while self-pollination occurs when a flower fertilizes itself without external help.
Plant breeders and seed savers work with several categories of varieties worth understanding. An open-pollinated plant is naturally pollinated and produces offspring that are true to type, meaning saved seeds grow into plants very similar to the parents. Heirloom varieties are open-pollinated plants with a long, often generations-deep history. Hybrids are the offspring of two different parent varieties, commonly labeled F1 for the first filial generation. GMOs, or genetically modified organisms, are created through laboratory techniques that directly alter a plant's DNA. Choosing among these depends on gardening goals, whether preserving heritage traits, achieving specific qualities, or exploring modern breeding.