You may come across the word "true leaves" when reading information on seed packages and other garden-related literature. If you're anything like me, you're probably wondering what the hell that means and whether or not there are fake leaves. When seedlings sprout, two pairs of leaves usually appear first. They resemble a four-leaf clover. However, these are not true leaves because they do not remain on the plant after it grows shoots. Instead, they fall off once their purpose is served.
After the seedlings grow some more, new leaves will emerge from the stem. These are called major leaves and they can be any color or pattern. However, they all will eventually wither and die unless you plan to keep them as plants in your garden.
Finally, if the seedling is going to be a female plant, it will have ovules (female organs) inside its major leaves. If it's going to be a male plant, it will have pollen (male organs) when it blooms. Pollen can travel on wind currents for many miles so be careful where you put those flowers!
That about covers it for the difference between true and false leaves. There are many more types of leaves besides these two examples but this should give you an idea of how leaves help green up the world around us.
A "genuine" leaf is one that is capable of photosynthesis, the process through which plants produce their own food. When a seedling sprouts, the first leaves to develop are "cotyledons," or seed leaves, rather than "real" leaves. True leaves have the appearance of mature leaves, whereas cotyledons are basic and unremarkable.
True leaves contain three main types of cells: vascular cells, sclerenchyma cells, and parenchyma cells. The vascular tissue provides support for the leaf and carries water and nutrients from the roots to the rest of the plant. Sclerenchyma is hard, thickened tissue found in some seeds and young plants that helps them withstand wind, rain, and snow damage. Parenchyma cells are the most abundant type of cell in leaves, making up approximately 95% of all cells. They play a key role in gas exchange, so they need to be present in sufficient numbers to allow for effective oxygenation of the plant's blood and carbon dioxide absorption during photosynthesis.
Leaves also contain several important chemicals that protect plants against insects and other organisms that would eat them. These defenses include toxic substances such as cyanide, resin, and oils, along with signals that warn predators away from its fruit/seed pods.
Finally, leaves provide physical support for the rest of the plant and act as an interface between the plant and its environment. They can be almost any shape but are usually flat or folded.
When a seed emerges from the soil or potting mixture, it has a pair of leaves known as cotyledons. The cotyledons are a component of the seed that serves as a food supply for the sprouting seedlings. As the seedling grows, the cotyledons will develop into photosynthetic mature leaves. When the first flower appears, you can say that the plant is transitioning to its reproductive stage. This is called bolting in garden terms, and it means that the plant will soon stop producing new seeds and begin generating fruit instead.
The first flower that appears is called the main shoot's terminal head. This is followed by several pairs of lateral shoots, or petioles. These will eventually grow into the flowering branches of the plant. Between each pair of lateral shoots is a node. You can think of a node as a little bump on the stem where two branches join together. Above the primary shoot are the secondary shoots. They will also develop into flowers and branches. Finally, there are the tertiary shoots, which do not produce flowers but rather pods containing small brown seeds.
So, a flowering plant will produce three sets of true leaves: one pair of cotyledons, then several pairs of lateral shoots, and finally the terminal heads with their floral buds, which will open to form the fourth set of leaves.
The solitary seed leaves of monocots, such as grasses and lilies, are typically buried. True leaves emerge above the cotyledons on the seedling and resemble a miniature replica of the plant's adult foliage. The appearance of these seedlings is what first attracts attention to them.
Once the seed has been planted, it is exposed to soil conditions. If the seed is planted in rich soil, the seed will grow a shoot that will eventually produce more seeds. If the seed is planted in poor soil, the seed will not grow because there is no food for the young plant. This is why seeds are usually planted in soil with good germination properties to ensure success.
Monocots have separate male and female plants. The pollen is carried by wind or insects to reach the ovules of the next generation. So plants must be pollinated if they are to reproduce.
Seed-derived monocots can reproduce both sexually and asexually. Animals, weather, and humans can all help spread their seeds far and wide. Plants use different methods depending on their environment and what type of reproduction they want to achieve. For example, some species of palm will spray droplets of water containing sperm cells onto their flowers to fertilize them. These seeds then fall to the ground where they begin new plants.