Plant Transport and Physiology

Plants can absorb nitrate or nitrite from the soil via their root hairs. If nitrate is absorbed, it is first reduced to nitrite ions and Ammonium ions for incorporation into various compounds.

The external protective layer in dicot root is called as epiblema or piliferous layer. The cells of epidermis extend into unicellular root hairs. In the root cap there is no root hair present. In absence of root hairs water absorption is not possible. So, the correct answer is option B.

Epiphyllous buds (adventitious buds) develop on the margins of leaves in plants like Bryophyllum. These buds serve as a means of vegetative reproduction, allowing the plant to grow into new individuals.

Phloem is responsible for transport of food and minerals. Food synthesized in photosynthetic parts is translocated to nonphotosynthetic parts through the phloem. Phloem translocates organic substances and inorganic solutes first from leaves to all other parts of the plant and storage organs. Storage organs re-export organic nutrients to those parts which require the same as newly formed leaves and fruits i.e., it is bidirectional.

The food manufactured in the leaves is translocated upwards and downwards. And to all the parts of the plant through its phloem. The phloem conducts some other substances like amino acids. The conducting cells of the phloem are cylindrical cells known as sieve tubes. These partitions are known as sieve plates. Sieve elements are the food conducting cells of many phloem tissues. Sieve elements in angiosperms are the sieve tubes, while in gymnosperms and pteridophytes, these are sieve cells.

So, the correct answer is option B.

In plants, phloem tissues perform the function of  conduction of food.

• Phloem is the vascular tissue responsible for the transport of sugars from source tissues (e.g., photosynthetic leaf cells) to sink tissues (e.g., non-photosynthetic root cells or developing flowers). 
• Other molecules such as proteins and mRNAs are also transported throughout the plant via phloem. Phloem is composed of several cell types including sclerenchyma, parenchyma, sieve elements and companion cells. 
• The sieve element and companion cell are found closely associated with each other in what is referred to as the sieve element/companion cell complex. One or more companion cells may be associated with a single sieve element. 

In-plant food is transported through the phloem.

Xylem is a type of vascular tissue in plants that transports water and solutes from the roots to the leaves. Phloem is the vascular tissue in plants which conducts sugars and other metabolic products (food) upward and downwards from the leaves.
Thus, the correct answer is option B.

• Vascular tissues make up the organs that transport water, minerals, and food throughout the plant. Vascular tissue can be divided into two functional units. Xylem transports water and minerals from root to shoot. 
• Phloem transports nutrients (such as sugar and amino acids) from leaves and other production sites to roots, flowers, stems, and other tissues.

Phloem tissue is responsible for translocation, which is the transport of soluble organic substances, e.g., sugar. The substances travel along sieve elements, but other types of cells are also present: the companion cells, parenchyma cells, and fibres.

The food manufactured in the leaves is translocated upwards, downwards and laterally to all parts of the plant through the phloem. The phloem also conducts some other substances such as amino acids. The conducting cells of the phloem are cylindrical cells called sieve tubes, which have sieve like partitions at both ends. These partitions are called as sieve plates. 

Xylem tissues include tracheids, vessels, fibres and parenchyma and serve in the ascent of sap/water and minerals. Phloem tissues is a composed of four elements namely, sieve elements, companion cell, phloem fibres and phloem parenchyma and serve in translocation of organic nutrients. Transfer RNA (tRNA) serve as carrier RNA and transports amino acids from cell pool to the mRNA bound to the ribosome where the protein is being synthesized. Haemoglobin molecule contains four polypeptide chains and four heme prosthetic groups. It serves as a carrier of oxygen gas. 

Phloem tissue is responsible for translocation, which is the transport of soluble organic substances, for example, sugar. The substances travel along sieve elements, but other types of cells are also present: the companion cells, parenchyma cells, and fibers.