Plant Propagation Techniques

Vernalization is the process of inducing flowering to a plant by exposing the plant to cold of winter or through artificial processes. The process of Vernalization converts a biennial into an annual and spring variety into a winter variety and an annual into a perennial.

During spring season the cool-season crops plants have enough time to reach maturity before the weather turns warm. Vernalization if the process of cooling the seed to germinate and induce flowering process.

In the case of potato, it requires more photoperiod to induce flowering. Whereas for the formation of tuber, it requires very less photoperiod. Thus, it is told that potato is LDP for inducing flowering; but SDP for tuber formation. The flower-inducing florigen and tuber-inducing tuberigen signals are functionally exchangeable. Flowering and tuberization are distinct reproduction strategies, both of which involve the sensing of the photoperiod and generation of a signal in the leaves (process called as induction), the subsequent transport of the signal (known as florigen or tuberigen), and the response in a distant organ, the vegetative meristem, or stolon tips (also called evocation).

Growth is an irreversible increase in the size. There are three developmental stages of growth of all plant parts including shoot and root. These are cell division, cell enlargement and cell differentiation. Cell division is the first phase that results in increase in the number of cells. In plants, karyokinesis, division of nucleus is followed by cytokinesis, the division of the cytoplasm. Cell enlargement gives the proper size to the organ and tissue. During this, protoplasm, vacuole, etc are formed. Cell differentiation is seen at cell level, tissue level, organ level and at the level of an organism. The cells differentiate to form different types of tissues that later perform different but specific functions.

The portion of pith taken as an explant comprises of parenchymatous cells (i.e., simple permanent tissue which have lost the capacity to divide). When such cells are cultured on solid culture media, the parenchymatous cells of pith become meristematic and start dividing resulting in a mass of undifferentiated cells called callus. This is an example of dedifferentiation. 

In plants, apical meristems divide and differentiate to perform a specific function. This phenomenon is called as differentiation. Sometimes, the differentiated cells in plants regain the capacity to divide under certain conditions. This phenomenon is called as dedifferentiation. An interfascicular vascular cambium is an example of dedifferentiation. During dedifferentiation, certain cells lose the capacity to divide and becomes mature. This phenomenon is called as redifferentiation.

The phenomenon of generation of whole plant by single cell is totipotency.

Grafting is a technique whereby tissues from one plant are placed or inserted into another in such a way that the vascular tissues of both the plants may join together. The plant which is selected for its roots is called as the stock and the one selected for its stems and leaves and flowers is called as the scion. For successful grafts, the events that should take place is the production of the callus tissue between the cells of the stock and scion. 

A group of organisms, genetically related with one another and are formed from a single parent by means of asexual reproduction. In the genetic clone, all progeny are morphologically and genetically related with one another.

So, the correct answer is 'plants produced by asexual means’

They are generally propagated by vegetative to produce offsprings which are practically clones of their parent plants. If a plant has favourable traits, it can continue to pass down its helpful genetic information to its family. This is especially economically advantageous as it allows commercial growers to clone a particular plant to ensure consistency throughout their crops.

Thus, the correct answer is C.

The genetic material from wild varieties can be preserved either in gene banks or in-situ preservation. Gene bank saves the genes and other regenerative material from a wide range of plants. In-situ, is the preservation of wild variety of plants in the fields and forests where they grow. Thu, the correct answer is option A.

Totipotency - The ability of cells such as an embryonic stem cell to differentiate into any type of body cell. Plant cells are also totipotent, which helps to explain why a graft of a plant can generate a whole new individual out of just a small branch cutting.
Totipotent cells can form all the cell types in a body, plus the extraembryonic, or placental, cells. Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are totipotent. Pluripotent cells can give rise to all of the cell types that make up the body; embryonic stem cells are considered pluripotent. Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells; adult stem cells and cord blood stem cells are considered multipotent.

Plant breeding programs aim to improve crops in multiple ways. This includes developing varieties that are resistant to diseases, produce higher yields, and mature earlier to optimize farming cycles.

The prime aim of plant breeding is to improve the characteristics of plants that they become more useful automatically and economically. Some of the objectives may be summarized as follows-
1. Higher yield: Higher yield of grain, fodder, fibre, sugar, oil etc.
2. Improved quality: The quality characters may vary from one crop to another, such as grain size, shape, colour, milling and backing quality of wheat, cooks quality in rice, malting in barley. Size shape and flavour in fruits and keeping quality of vegetables, protein contents in legumes, methionine and tryptophan contents in pulses etc.
3. Disease and pest resistance: Resistant varieties offer the cheapest and most convenient method of disease and pest control. They not only helps to increase the production but also stabilize the productivity.
4. Maturity duration: It permits new crop rotation and extends crop area. Thus breeding for early maturing varieties suitable for different dates of planting. This enables the farmer to take two-three crops in a year.
5. Agronomic characters: Three includes the characters, such as dwarf, profuse tillering, branching erect resistance and fertilizer responsiveness. Thus, option D is correct.