A seed is an undeveloped embryo of a plant, which is enclosed in a protective outer covering. It is a food reserve of the plant, and is usually formed from a part of the plant, such as a tuber or husk.
Gymnosperms
Gymnosperms are a group of plants which produce naked seeds. They are classified as vascular plants and are important to ecosystems. This group includes conifers, hemlocks, cycads and ginkgo. Approximately one thousand species are found around the world.
Gymnosperms differ from angiosperms in the way they develop their seeds. Angiosperms begin with double fertilization, whereas gymnosperms start with single fertilization. Each seed contains an embryo.
Gymnosperms also have a different reproductive cycle from angiosperms. The gametophyte of angiosperms is enclosed in the ovary, whereas the gametophyte of gymnosperms is not enclosed. As a result, the gametophyte’s lifespan is shorter.
Among the two types of Gymnosperms, monocotyledons are composed of an endosperm and a sporophyte. Monocotyledons include palms, grasses, legumes and trees.
During meiosis, the male and female spores are released into the air. These are then carried by wind and other animals. When pollen meets sperm, the two cells fuse, forming a zygote. Depending on the amount of free water available, the zygote may be aborted or may develop into an embryo.
Angiosperms
Angiosperms are one of the largest groups of plants. They are an important part of the terrestrial ecosystem. Many of the foods we consume are angiosperms. They have become extremely diverse because of the multiple interactions they have with animals. These species live on land, water, and in the air.
In order to reproduce, angiosperms must have a pollinator. Pollination takes place by wind or by other mammals. There are two types of pollination: self-pollination and insect-mediated pollination. The flowers of angiosperms are designed to attract insects.
During the flowering period, angiosperms produce pollen. This pollen is small in size. However, it is more readily distributed than gymnosperm pollen. As a result, it is easier to fertilize another flower.
In addition to producing pollen, angiosperms also produce female gametophytes. These gametophytes are able to produce fruit more quickly than gymnosperms.
Gymnosperm seeds
Gymnosperms are seed-bearing vascular plants. They are distinguished from angiosperms, which are flowering plants. There are approximately 1000 species of gymnosperms, which belong to 88 plant genera. These plants include conifers, pinophytes, cycads, and ginkgo. Many of these plants are important to terrestrial ecosystems, such as forests, wetlands, and rocky mountains.
Seeds are a key feature of many aspects of plant evolution. Seeds are also important as a means of dispersal. Unlike angiosperms, which develop in fruit, gymnosperm seeds can develop on leaves or scales. However, gymnosperms use pollen to fertilize their seeds. Pollination in gymnosperms is an anemophilous process.
The pollen grain is a small, cylindrical structure that consists of a generative cell and two prothallial cells. These cells form a tube that grows toward a megasporangium, a multicellular egg-containing structure. This tiny hole then oozes a sticky “pollination droplet”. When it reaches the female megasporangium, the droplet resorbs to form an egg.
Common seeds of commerce
Common seeds of commerce include a wide variety of items. These include pecans, hazelnuts, beans, sunflowers, and peanuts. Aside from food, these items are also important in human health as they contain stimulants and oils. They are also good for the environment.
Seeds are a small but important component of our diets. Their production is highly concentrated in the developing world. However, they are not always produced in a quality manner. Consequently, they are subject to the specter of contamination.
Luckily for consumers, seeds of the modern era are now protected by law. Business entities are obligated to procure and sell seeds that comply with legal regulations. The National Food Safety Agency (ANSA) issues biological value certificates and quality certificates for seed exports.
As with other aspects of the agricultural industry, the most effective way to increase yields and improve crop health is through improved seeds. This can be accomplished through a combination of research, technology and training.
Germination
Germination of seed is a crucial stage of the plant life cycle. In germination, the embryo within the seed grows into a root and a shoot. The process is governed by environmental conditions such as temperature and oxygen. There are four main stages: imbibition, emergence, growth and development of the embryo into a seedling.
During germination, a number of bio-physical processes are performed such as uptake of water, growth of the root system, and mobilization of food reserves. Seeds need adequate oxygen for optimal germination. When these nutrients are unavailable, a seed can become dormant. Therefore, understanding the dynamics of germination at the high end of the temperature spectrum is important. This knowledge is also essential for biodiversity preservation.
A study was carried out to evaluate germination of 15 accessions at constant temperatures of 5 and 21 degC. Results indicated that the majority of accessions had relatively low germination rates at 5 degC. At 21 degC, a greater percentage of accessions had high germination rates.
