Transport in vascular plants - class-X

Photosynthesis is the process by which green plants make their own food from carbon dioxide and water in the presence of sunlight. The prepared food is glucose. To prepare one molecule of glucose, by the process of photosynthesis six molecules of carbon dioxide and six molecules of water is required. Six oxygen molecule is released as a waste product. This oxygen is produced due to splitting of water by the process of photolysis during light reaction. So, the correct answer is option 'Oxygen'.

In physiology, respiration is defined as the movement of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction. The physiological definition of respiration should not be confused with the biochemical definition of respiration, which refers to cellular respiration. The metabolic process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and 38 ATP (energy). Although, physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the bulk flow and transport of metabolites between the organism and the external environment. 

Lenticels are involved in gaseous exchange between internal tissues and atmosphere. These are porous tissues present in periderm that are developed during secondary growth.

The highest rate of respiration are found in the actively growing root and stem tips, cambium and embryos of germinating seeds and lowest rates in dormant seeds or spores. As, the growing tips are generally rich in meristematic tissues the rate of respiration is also high.

Out of all the options given the third option is the correct one.
Exchange of gases is a feature that is common in all living things. Irrespective of the genera of living organisms,  all organs that exchange gases are characterized by features such as- thin, moist, large surface area and a large capillary network.

All parts of the plant respire, the leaves, the stem, the roots and even the flowers. The parts above the soil get their oxygen directly from the air through pores. The pores in the leaves are called stomata. The pores in stems of trees are called lenticels.

Photosynthesis does not take place in plants during night time as the sunlight is absent and the accumulation of carbon dioxide is more. we feel suffocated if we sleep under trees during night times are more carbon dioxide is present around the trees.

Source and sink are important concepts in translocation in plants. In plants, organic solutes are translocated from regions of their synthesis like green leaves or storage organs like tubers in stem and roots to the region of their active utilisation like the regions of active growth at tips of stem and roots. Thus green leaves and storage organs act as source, whereas regions of active growth act as sink for organic solutes.

The translocation of sugars in a plant occurs from source to sink by active loading at source or supply end and active unloading at the sink end. The source and sink are not fixed and keep on changing depending on the physiology of plant. In water transport water is always transported from roots to the aerial parts but not so in case of sugars. 

In plants sugars are translocated by phloem tissue. This can be experimentally demonstrated by girdling experiments. In girdling experiments all tissues from phloem to epidermis, including secondary phloem are removed. This stops flow of sugars to plant parts below the level of girdle. Thus, the roots are starved and consequently the plant is killed.

Plants photosynthesize to produce sugars. Sugars are produced as monosaccharides- glucose or fructose. They are transported in the disaccharide form of sucrose through phloem tissue. Sugars are stored as polysaccharides, starch in storage organs.

The absorption of water and minerals from the soil by the roots of plants and their movement inside roots of the plant and subsequently its upward movement in stem and other aerial parts of the plant body is because of the following phenomenon:-
Imbibition
Diffusion
Osmosis
Osmotic pressure
Root pressure
Turgidity and flacidity
Plasmolysis and deplasmolysis 

The absorption of water and minerals from the soil by the roots of plants and their movement inside roots of the plant and subsequently its upward movement in stem and other aerial parts of the plant body is because of the following phenomenon:-
Imbibition
Diffusion
Osmosis
Osmotic pressure
Root pressure
Turgidity and flacidity
Plasmolysis and deplasmolysis

In ringing experiment a complete ring of tissue is removed outside the vascular cylinder at a particular height from ground in a dicot plant. As the xylem is intact water can move freely to the aerial parts from roots. But the sugars cannot move down to roots from aerial parts, because of the removal of phloem tissue, which occurs in the outer cylinder and is removed in ringing experiment. 

The increased contents within the cells exert a high amount of pressure on their wall. This pressure moves the food material to the adjacent cells with low pressure. This allows the phloem to move material according to the plants needs.

There are two types of vascular tissues present in the plants viz. Xylem and Phloem. Xylem is responsible for transport of water and some minerals. Phloem is responsible for transport of food and minerals.

Root pressure provides a force which causes pushing of water in a stem. A continuous flow of water is maintained in the plants because the leaves transpire water through stomata and to replace the lost water the water drawn by the roots moves up.

Leaching is draining away from soil, ash, or similar material by the action of percolating liquid, especially rainwater downwards.

Xylem transport is primarily unidirectional (roots to leaves) due to transpiration pull. Phloem transport is bidirectional (source to sink), as sugars can be moved to various parts of the plant depending on metabolic needs.

Apoplast and symplast are two routes used by plants to transport water from root hair cells to the xylem of the root. Apoplast includes the non-living components of a plant such as cell walls and the intracellular spaces. The main difference between apoplast and symplast is their mechanism of the water movement.

The movement of water and minerals in xylem and the movement of phloem sap in phloem is unidirectional and bidirectional respectively. Plants need water for their growth, and it uptakes water through the roots. Water that is taken by the roots has to reach all the leaves or branches, here the xylem function as transportation of water. Therefore, the movement of water and minerals in xylem is always an unidirectional. Whereas, the movement of phloem is bidirectional this is because, once the food is synthesized it is the phloem that transfers the food to all the parts of plants wherever it is necessary.

 For plants to take up mineral ions, ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil. Active transport (pumps) then occurs across the root so that the plant takes in the ions it needs from the soil around it. The root hair cells have carrier molecules on their surface that pick up the minerals and move them into the cell against the concentration gradient.

(A) The upward flow of the water is seen in the roots of the plant.

Plants absorb their mineral salt supply from the soil through the roots from the zones of elongation and root hair. The minerals are absorbed as ions which are accumulated by the plants against their concentration in the soil.

Solar heat causes the evaporation of water from the surface of the leaves in form of water vapour through small openings called stomata. This loss is known as transpiration. Due to the loss of water, water stress condition is created that forces the upward movement of water from the soil towards the shoot system. This water is then again distributed to various plant parts.