A seed is a random value used in computer programming, encryption, and other software. A seed can be hardware information, date or time, or other values that help generate a random value.
A seed contains an embryonic plant with a food supply enclosed in a protective outer covering called a seed coat. Cecilia and her colleagues at The New York Botanical Garden are studying how genes control ovule and seed development in gymnosperms and angiosperms.
Germination
The process of germination is when the seed breaks out of its protective shell or embryo. It then begins to grow a root and shoot, and grows upwards in search of sunlight. Then it is able to use food it has stored as energy for growth and reproduction. The process of a seed germinating is also known as cellular respiration.
Most seeds require a significant amount of water to begin the germination process. This is because the seeds often carry a large food reserve such as starches, proteins, and oils. These reserve foods are broken down by enzymes in the seed, which are activated when the seed imbibes water. This process is known as imbibition.
Federation University Australia, seed ecology laboratory has found that alternating temperature conditions enhance the germination of Nassella trichotoma seeds. The seeds were buried in a mesh bag at different depths. The germination percentages observed were then compared to those under complete darkness and alternating light and dark photoperiods.
Dormancy
Dormancy is a period of inactivity, much like hibernation for a bear or the winter dormant state of certain plants. Dormancy allows living things to survive harsh environmental conditions that they cannot tolerate otherwise.
There are two kinds of dormancy in seeds: physical and physiological (see Figure 3.4). Seeds with physical dormancy have one or more water-impermeable layers of palisade cells within the seed coat that prevent radicle emergence from the endosperm. This kind of dormancy can be broken by scarification, a process in which the hard seed coat is physically damaged so that radicle emergence is allowed.
Plant physiologists have discovered that a number of chemical and physical treatments can stimulate seed dormancy. These include heat, light and hormones. Some treatments are very short-lived, but others are longer-lasting and may allow the seed to germinate for several years. Long-term effects of temperature are also important, and cyclical variations in climate may influence seed dormancy on a seasonal or annual basis.
Imbibition
The imbibition of water by seeds or other objects is a complex process. The imbibed substance increases in volume due to the attractive intermolecular force between water and the imbibing material. This force is called the matrix potential or imbibition pressure. This is the reason why dry seeds swell when they are soaked in water and wooden frames swell during rains.
The imbibed seed also absorbs other substances from the imbibing medium. This causes the seed to swell and crack open its outer coatings. The degree of cotyledon cracking is proportional to the rate of imbibition. Hence, it is necessary to control the rate of imbibition in order to ensure that the cotyledons remain intact.
In the present study, imbibition of lima bean seeds was measured after exposure to various metal salts. It was observed that nitrate enhanced imbibition and germination. This was due to the increase in ABA production in the seed during early imbibition. This reflects the role of ABA in maintaining dormancy in imbibed seeds.
Photosynthesis
Photosynthesis is the process by which plants release sugars into the atmosphere and absorb carbon dioxide from the air. A plant’s pigment molecules, called chlorophyll, absorb light energy from the sun, which it uses to split water molecules into hydrogen and oxygen. The oxygen is released into the air, while the hydrogen becomes glucose or other sugars that provide food for the seed and its roots and leaves.
The glucose also provides the energy needed for germination. A seed’s carbohydrate reserves are used to keep it alive until it can perform its own photosynthesis.
All plants and blue-green algae possess chloroplasts, green-coloured cell organelles that contain the enzyme photosynthesis. These cell organelles are located in the mesophyll cells of leaves and flowers, which make up the green parts of plants. The first stage of photosynthesis, which releases oxygen, is often referred to as Hill’s reaction after the Swiss botanist who developed it in the early 1900s.