INTRODUCTION TO THE BIG WORLD OF PLANTS
Plants provide a lot of variations in form of flavor, scent, and texture, so they really form a base of our food history and tradition. Although many people neglect their eating of plants, our human bodies are still dependent on the chemicals that plants provide to keep our health and protect us from many awful diseases, including cancer and atherosclerosis. The big plant kingdom includes not only vegetables and fruits, but also nuts, legumes, seeds, and grains - all of which the human beings learned to appreciate and cultivate.
As you might know already from your biology classes, plants are autotrophs, that is they can sustain themselves on the simple molecules that are widely available around them - carbon dioxide, water, and sunlight being the main constructors of plant life. Plants have an inherent ability to convert these two seemingly noninteresting food molecules into sugar, and further into other molecules that provide color, flavor, and fragrance. This method of metabolism has shaped the plants, as they are perfectly constructed for acquiring of their food molecules: their roots go deep into the soil to capture water and minerals, their leaves are broad to capture as much sunlight and carbon dioxide as possible, and their stalks are usually high enough to get conveniently close to the sunlight. For these reasons, plants don't need to move and can stay implanted in the soil for all their lives. This is of course disadvantageous when it comes to protect oneself against enemies (can't run away) but the plants have their own defense mechanism in form of certain toxins or badly smelling molecules that animals tend to avoid. This is of course not without exceptions, as we humans tend to like the otherwise strong and rejecting fragrance and taste of e.g. onions, garlic, or fennel. However, we and other animals have learned to use such plants in the quantities or in preparations that reduce and actually entice our taste buds.
The beautiful flowers and juices of may plants are there to ensure the reproduction, but not by attracting the opposite sex but rather by attracting insects that would spread their germlines to other individual plant, in favor of providing the nutritious juices to the animal. Funny how love is. As soon as one male pollen is spread to a female ovule on another plant, a seed can start to grow. This seed is then about to by implanted into soil, but it cannot be placed in any place among plants that are already grown and could compete too well for the sun and water. The seeds can therefore be spread by the wind, as some of them may be attached to a light propeller that would carry them away from an overgrown plant population. Of course, such form of reproduction is highly dependent on chance, but the plants often compensate for it by producing many seeds and thus increasing the probability of successful reproduction. What about seeds in fruits? These are just another way of securing the reproduction for a plant. As an animal eats a tasty fruit, the seeds will pass into its digestive system and, while the animal is moving from place to place, allow the seed to travel as well before it is passed out together with a pile of animal feces, which is, by the way, full of nutrition that a plant seed can benefit from. The timing of eating a fruit is also crucial - the seed within the fruit must be mature before it can be used to produce a new plant. This is also the meaning behind fruit ripening: when the fruit meat is at its best, the animal will eat it. At this point in time, the seed is also mature and ready to become a new plant.