Reproduction in plants

Reproduction in plants

March 16, 2018

Reproduction in plants

The flower is the reproductive organ of the plant. It usually contains male organs (pollen containing pollen containing sperm) and female organs (an ovary containing eggs, from which leaves a leaf and a scar in the head). After fertilization, ovulation with the eggs develops into fruit with seeds.

This process, known to us from many ornamental plants, belongs to the large and widespread group of plants called "semen-covered" plants. These are plants with flowers, whose seeds are packed and sealed in fruit tissues, such as orange and apple. It is an evolutionarily young group. Its prominent representatives appeared only about 123 million years ago (the Cretaceous era), and became the most common and diverse group about 85 million years ago. Their success stems from the nature of their reproductive system, which includes, as stated, the flower and the fruit.

The development of the various flowers allowed for the first time in evolution the efficient and accurate transfer of pollen (sperm) by insects and other animals from one plant to another. This is a process of great importance in plants, which are mostly rooted, immobile, and devoid of behavior. Transferring the pollen between the plants allows for crossbreeding and essentially the "genetic cards" and the creation of genetic diversity. This diversity has created new genetic species with adaptations to a variety of habitats that have spread to new places.

The flower is basically made up of leafy limbs. The bud of the flower differs from the leaves' sprouts in a certain growth and the activity of the bud Amiri for a certain period of time. The leaves are characterized by indeterminate growth that can last for a long period of time. In the primitive flowers, the flower organs are arranged along the flower axis in a single thread, like in magnolia. On the other hand, with more elaborate flowers, the flower organs are organized in pairs as in the color. At the same time, there is no bud in the bosom of the flower leaves, as in the bosom of leaves along the stem. The differentiation of the bud into leaf or flower is subject to genetic, chemical and environmental control. Depending on the plant's reaction to different environmental conditions (ie, what stimulation they need to change the direction of differentiation), distinguish between long night plants (short day plants) and short night plants (long day plants) and plants that are indifferent throughout the night. The entire reaction is known as photoprodism.

 

In Magnolia, which is considered a keduma, the flower bed is long and conical, and the flower parts are large and numerous. Most of the flowers are considered to be more developed, with the flower axis shortened, its joints dense, and the number of flower organs (sepals, crowns, struggles and ovarian leaves) is significantly reduced. In a typical flower there are four types of organs whose function has changed. Although not always find them all in the flower but their order from the outside in fixed. An extreme example of a flower in which some of the organs are missing is the carob tree, which lacks sepals and crowns, and only the genitals have been preserved.

 

The four organs of the flower:

(1) The calyx (sepals) forming the cup (calyx) constitute the outer generation of the flower casing. Grape leaves are usually green and resemble regular leaves, they protect the inner parts of the flower.

 

(2) Petals build together the title (Corolla). These are usually colored leaves that advertise the flower and attract insects or other animals. Many flowers have evolved in the title of cloves that secrete nectar that is used to reward food for insects and other visiting animals. Many petals have models (punctuation, misses or spots) that direct the insects to the location of the codes or area of ​​the pollen (which are sometimes also a source of food). A distinction is made between a header from a joint that is formed by the fusion of the single petals on the edges (eg, bewilderment) and a separated title (eg rose). The title is correct when the petals are the same and the flower has circular symmetry (eg, adenium). The irregular title is when there are differences between the different petals in form, size and position, and the flower has only one symmetry plane (eg, a fragrant patina). The differences in the title between the various plant species evolved in parallel evolution to the development of different pollinating animals (mainly insects). In general, the number of petals is usually the same as the number of cups and their position - alternately with the cup leaves.

 

(3) Stamens - which form the organ in which the male sex cells are formed and from which they disperse during pollination.

 

(4) Carpels - the organ in which the female sex cells form and then develop into the whole or part of the fruit.

 

All four flower organs are connected in a fixed order on the flower axis, known as the receptacle. Part of the stem that connects the flower substrate to the plant is known as the pedicel.

Inflorescences

Along with the evolutionary trend to reduce and simplify the structure of the flower, the semen appears to have a tendency to group the flowers into different forms of inflorescence - for example, the scalp in the complex family, the awning in the family of the success, or the oatmeal in all these examples. In some of the inflorescences, there is a division of labor between flower groups in different locations, such as fruitless flowers at the edges of a round flower that play a role in attracting pollinators, such as in leafy Moran or hydrangea. And like the flowers in the head, the inflorescence of frivolous rescuers.

Pollination

The pollen grains do not reach the eggs directly, but are captured by a scar - a special organ that forms and develops from the ovary leaves. The transfer of pollen grains from the struggle to the scar is called "pollination." Most semeners are mutually polluting, but self-pollination is not uncommon. It is a relatively safe route, compared to pollinating insects or other animals. Pollination or self-fertilization is common in certain habitats, annuals, or certain types of trees such as Aesculus. This breeding model is also found in invasive plants or pioneer plants. In this case, a single plant is enough to create an entire population.

However, many species have developed a physiological or morphological mechanism that is essentially a prevention of self-pollination through self-sterility or hereditary self-incompatibility. Other plants have a preference for foreign pollen (from other plants) but in the absence of foreign pollen, there is a self-pollen (of the same plant).




Also in Garden Seeds News

Fertilizer
Fertilizer

August 02, 2019

Read More

prune trees
prune trees

July 18, 2019

Read More

Plants & digestion
Plants & digestion

June 21, 2019

Read More