Germination is the start of the growing process for a plant embryo. There are a host of internal and external factors that have to be in place in order for germination to occur. Most seeds require some period of dormancy before they will germinate. This can come about by either physiological or mechanical methods or both. Some seeds can break dormancy by scarification which involves artificially cracking the seed coat. In nature, seeds may require a period of freezing and thawing in order to crack the seed coat or passage through an acidic digestive tract. In most woody plants in temperate regions, a cold period is required before growth will commence. Some plants will absorb vast amounts of water which instigates the activity of enzymes before germination begins. When the seed is waterlogged oxygen may be reduced and anaerobic respiration may occur until the seed coat cracks and oxygen is admitted to the embryo. In most cases, the temperature is vital to germination. Light roles in germination vary depending on the kind of plants involved. Some lettuce seeds, for example, will not germinate in the dark, whereas some seeds such as the California poppy will only germinate in the dark.
There are all sorts of flower shapes, sizes, colors, and arrangements; however, there are a few features that are central to all flowers regardless of their form. A flower starts as an embryonic primordium that develops into a bud and it is situated on a specialized branch at the end of a stalk called the peduncle. The receptacle is a small pad-like swollen area on the very top of the peduncle. This serves as the platform for the flower parts. Whorls, which are three or more plant parts, are attached to the receptacle. The sepals are the outermost whorl and are usually green. Sometimes they are confused with leaves. They are usually three to five in number and are collectively referred to as the calyx. The second whorl of flower parts are the petals and are collectively referred to as the corolla. The corolla is usually extra-showy in order to attract pollinators. In wind-pollinated plants, the corolla may be missing to maximize pollen exposure to the female flower parts. Just as the sepals in the calyx, the petals in the corolla may be fused together or occur as separate individual units. Nestled inside the two outer whorls are the sexual organs of the flower. The stamens entail the male structures: a semi-rigid filament with a sac called the anther dangling from the tip. Pollen grains develop in the anthers. Most anthers have slits or pores on the sides to accommodate pollen release. The female organs are collectively referred to as the pistil and include a ‘landing pad’ at the top called the stigma, a slender stalk-like style that leads down to the swollen base called the ovary. The ovary is what will develop/ripen into a fruit.
As you might have guessed, there are names for the different ways that the flower parts are arranged with respect to the ovary. The ovary is said to be superior if the calyx and corolla are attached to the receptacle at the base of the ovary. However, if the receptacle grows up and around the ovary and the calyx and corolla are attached above it, then the ovary is said to be inferior.
Inside the ovary is an egg-shaped ovule that is held in place within the ovary by means of a short stalk. The ovule is what develops into a seed. Fruits have seeds.
Some flowers are produced singly whereas others are produced in clusters called inflorescences. An inflorescence is characterized by one peduncle with many little stalks serving individual flowers. The little stalks, in this case, are called pedicels, and each stalk services one flower.
