Students can go through AP Inter 2nd Year Botany Notes 1st Lesson Transport in Plants will help students in revising the entire concepts quickly.
AP Inter 2nd Year Botany Notes 1st Lesson Transport in Plants
→ J.C. Bose designed a very sophisticated instrument called ‘Crescograph’ which was so sensitive that it could record even a minute growth of a plant upto a millionth part of a millimetre.
→ Bose research institute is at Kolkata.
→ Transport over longer distances proceeds through vascular tissues and is called Translocation.
→ In rooted plants, transport in xylem is essentially unidirectional from roots to the stems.
→ Organic and Mineral nutrients however undergo multidirectional transport.
→ The movement of gases or liquids from a region of high concentration to a region of lower concentration is called Diffusion.
→ Concentration gradient must already be present for molecules to diffuse even if facilitated by the proteins. This process is called Facilitated diffusion.
→ Active transport uses energy to pump molecules against a concentration gradient.
→ Water is essential for all physiological activities of the plant and plays a very important role in all living organisms.
→ A mature com plant absorbs almost three litres of water in a day while a mustard plant absorbs water equal to its own weight in about 5 hours.
→ Water potential = Solute Potential + Pressure potential.
→ The water potential of pure water is zero.
→ Solute potential is always negative.
→ Pressure potential is always positive but in plants it is negative.
→ Movement of water across a semipermeable membrane from low concentrated place to high concentrated place is called Osmosis.
→ It can be explained by Thistle funnel experiment.
→ Plasmolysis occurs when water moves out of the cell and the cell membrane of a plant cell shrinks away from its cell wall.
→ The normal living cells when kept in Hypertonic solution become flaccid. In such cell the pressure potential becomes zero. Hence the water potential is equal to the solute potential.
→ Imbibition is a type of diffusion when water is absorbed by solids-colloids-causing them to enormously increase in volume.
Eg : Absorption of water by seeds and dry wood.
→ Proteins have very high imbibing capacities compared to carbohydrates. Thats why proteinaceous pea seeds swell more on imbibition than starchy wheat seeds.
→ Mass flow is the movement of substances in bulk from one point to another as a result of pressure differences between the two points.
→ Plants absorb water and move into deeper layers by Apoplast pathway or Symplast pathway.
→ Mycorrhiza is a symbiotic association of a fungus with a root system.
→ Loss of water in the form of water drops is called Guttation.
→ Root pressure does not play a main role in water movement in tall trees such as Sequoia semper-virens (Gymnosperm).
→ Cohesion-Tension-Transpiration pull of water transport was proposed by Dixon (1914).
→ Stomata which opens during day time and closes during night time are called Photoactive stomata.
→ In succulent plants, stomata opens at night and remain closed during the day time (Scotoactive stomata).
→ Levitt proposed K+ pump theory to explain the mechanism of opening and closing of photoactive stomata.
→ ABA, a natural Antitranspirant helps in closure of stomata in water stress conditions.
→ Transpiration is beneficial to plants in many ways. So it is considered to be ‘a necessary evil’.
→ Pressure flow or Mass flow hypothesis was proposed by Munch.