Seeds are the most important sowing material. Understanding the morphological structure and development and maturation process of seeds, and mastering the environmental conditions required for seed germination, is the basis for cultivating high-quality seedlings. In order to improve the germination rate and germination neatness of seeds, it is particularly important to master the appropriate seed treatment technology to properly treat the seeds before sowing.
<h1 class="pgc-h-arrow-right" data-track="1" > the structure and germination of seeds
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Seeds are developed from ovules and are the organs of seed plants that reproduce offspring. After seed germination, it forms a plant body with roots, stems and leaves, and then flowers, bears fruit, and produces new seeds. The seeds contain nutrients that can sustain life activities and germination for the embryo for a long time. Seeds are diverse in type and often carry appendages, and are often classified in agricultural production according to the origin and nature of the endosperm and appendages.
Mustard ovules
Classification is based on the presence or absence of endosperm
1. There are endosperm seeds
According to the degree of endosperm and cotyledon development and the source of endosperm tissue, it is divided into 3 types:
(1) There are many seeds with developed endosperm, and the embryos of such seeds only account for a small part of the seeds, and most of the rest are endosperm. Seeds of grasses, solanaceae, umbellifera and other plants.
(2) There are very few seeds that exist at the same time in endosperm and endosperm, such as pepper, ginger, etc.
(3) Seeds of the Amaranthaceae and Quinoa family with developed endosperm.
2. Endosperm-free seeds
During the development of such seeds, the nutrients are completely absorbed by the growing embryos. Therefore, the embryo of the seeds of such plants is larger, and there are developed cotyledons, such as peas, broad beans and so on.
There are endosperm and endosperm seed structure contrasts
Classification is based on seed appendages
1. Contains the fruit and its external appendages: nuts of the Quinoa family, lean fruits of the Family Tateshina, etc.;
2. Contains all fruits: coconut, strawberry, chestnut, carrot, celery, chrysanthemum, lotus, dandelion, etc.;
3. Contains a part of the fruit and seed (inner peel): peach, plum, plum, apricot, jujube, ivy, etc.;
4. Contains all the seeds:
It contains most of the plants: alliums of the lily family, melons of the cucurbitaceae family, cabbage, radish, kale, mustard greens, etc. of the cruciferous family, vegetable flowers of the Amaranth family, apples and pears of the Rosaceae family, beans, cowpeas, peas, etc., citrus, oranges, grapefruit, lemons, etc. of the family Rubiaceae, longans, lychees, etc. of the family Apocynaceae, grapes of the family Pulveridae, Morning Glory, tomatoes, peppers and eggplant of the Solanaceae family.
5. Contains the main parts of the seeds: ginkgo biloba, cycads.
Different vegetable seeds
<h1 class="pgc-h-arrow-right" data-track="1" > the morphology and structure of seeds</h1>
The morphology of the seed
Including the shape, size, color, surface finish, groove, edge, burr, reticule, waxy, protrusions, etc.; It is an important basis for identifying plant species and distinguishing the old and tender seeds from new and old; Mature seeds are darker and waxy, and young seeds are lighter in color and wrinkled; The new seeds are bright and smooth in color and fragrant, and the old seeds are gray and dark in color and have a musty taste; The seeds of the solanum are kidney-shaped, the seed coat of the eggplant is smooth, the seed coat of the pepper is thick and uneven, and the tomato seed coat is attached to the silver burr; Cabbage and cabbage seeds have similar traits, sizes and colors, and are spherical brown small seeds, with cabbage seeds having double grooves and cabbage seeds with single grooves.
The structure of the seed
Seeds are developed from fertilized ovules and are generally composed of three parts: embryo, endosperm and seed coat; The embryo is developed from the fertilized zygote, and the morphology of the embryo varies according to the crop type, the embryo of the bean seed is kidney-shaped, the eggplant seed is spiral-shaped, and the melon seed is upright; The endosperm of angiosperms develops after fertilization of the polar core, which is the storage tissue that supplies the nutrients needed for embryonic development; The seed coat is developed from beads and plays a protective role.
Phaseolus vulgaris seed structure
Tomato seed structure
Polyembryonic phenomenon
Plants usually have only one embryo, after sowing for a seedling, but some species of citrus, mango have polyembryonicity, in addition to containing a fertilized embryo in the seed, there are some asexual embryos produced by the division of bead heart cells, also known as bead heart embryos, after sowing often grow more than one seedling, the seedling maintains the genetic characteristics of the mother, and has great application value in genetic breeding.
Endosperm with cotyledons
During seed germination, the growth of young embryos relies on cotyledons and endosperms to provide nutrition and energy, and healthy seed embryos are bright in color and white in endosperm; Rotten or spoiled seed embryos become darker. Cotyledons not only store nutrients for seed germination, but also are the earliest assimilation organs that occur after the emergence of seedlings, and the size and development of cotyledons are very important for the cultivation of strong seedlings, and damage should be avoided.
<h1 class="pgc-h-arrow-right" data-track="1" > the development and maturation of seeds</h1>
Development of seeds
Mainly including the development of embryo and endosperm (or cotyledon); The development of the embryo begins from the fertilized egg, and the fertilized egg undergoes extremely unequal transverse cleavage after short-term hibernation, forming basal cells and parietal cells, which form the stalk and embryo body after several divisions, and the original embryo continues to divide and differentiate to form a complete embryo; Endosperm is developed by the development of a primary endosperm nucleus formed after fertilization of 2 polar or secondary nuclei of 1 sperm cell and a central cell, and the development of endosperm is slightly earlier than the development of the embryo.
Pumpkin seed development process
The maturation of the seeds
1. Seed physiological maturity
When the nutrients of the seed are stored to a certain extent, the seed embryo is formed, and the seed has the ability to germinate, which is called the physiological maturity of the seed. At this time, the water content of the seeds is high, the seed coat is not dense, it is not easy to prevent the loss of water, and it does not fully have the characteristics of protecting the seed kernel; At this time, the seed kernel shrinks sharply, which is not conducive to storage, and soon loses its germination ability, has poor ability to resist the external adverse environment, and is vulnerable to microbial invasion.
Wild fruit seeds
2. Seed morphology matures
The germ germ development is completed, the accumulation of nutrients is over, the water content is gradually reduced, the nutrients are transformed from the soluble state into insoluble fats, proteins and starches, the weight of the seed itself is no longer increased or increased very little, the respiration effect is gradually weakened, and the external form of the seed at this time completely shows the characteristics of maturity, called the morphological maturity of the seed; Seeds that have reached morphological maturity are dense, solid, and resistant to storage after entering a dormant state; In the process of transformation from physiological maturity to morphological maturity, a number of columns of biochemical changes occur internally, creating conditions for seed dormancy.
Mature dill seeds