Absorption by Roots

Question 1

need for water and minerals for plants

Answer 1

1. photosynthesis
2. transpiration
3. transportation
4. mechanical stiffness

Question 2

characteristics of roots to absorb water

Answer 2

1. huge surface area of roots
2. concentration of cell sap higher in roots
3. root hairs have thin walls

Question 3

five processes of absorption

Answer 3

1. imbibition
2. diffusion
3. osmosis
4. active transport
5. turgidity and flaccidity

Question 4

define imbibition

Answer 4

the phenomenon by which dead or living plant cells absorb water by surface attraction (substance made of cellulose or protein are hydrophilic- an important force in ascent of sap)

Question 5

define diffusion

Answer 5

free movement of molecules of substance from a region of higher concentration to a region of lower concentration when the two are in direct contact

Question 6

define osmosis

Answer 6

movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane

Question 7

define tonicity

Answer 7

when there are two regions of different concentration

Question 8

define isotonic

Answer 8

when concentration of water on both sides becomes equal

Question 9

osmotic pressure relation

Answer 9

osmotic pressure is equal to the weight or pressure equal to nullify osmosis

Question 10

define osmotic pressure

Answer 10

osmotic pressure of a solution is a measure of its tendency to take in water by osmosis

Question 11

define hypotonic and hypertonic

Answer 11

hypo- outside cell, lesser solute, leading to endosmosis
hyper-outside cell, more solute, leading to exosmosis

Question 12

define active transport

Answer 12

the passage of a salt/ion from a region of lower to higher concentration through a living cell membrane using energy from the cell
it is in a direction opposite to diffusion

Question 13

what are the ions that can’t pass easily through root cells and why?

Answer 13

nitrates, sulphates, potassium, zinc and manganese cannot pass through easily because there is a high concentration of solute inside the roots to promote osmosis. to obtain the ions, they have to be drawn inwards forcibly using energy provided by the cells

Question 14

define turgidity

Answer 14

the condition where a cell cannot accomodate more water, and is fully distended

Question 15

define turgor pressure

Answer 15

the pressure of the cell content on the cell wall

Question 16

define wall pressure

Answer 16

the pressure of the cell wall on the cell contents

Question 17

when the cell is turgid, the plasma mebrane…

Answer 17

is in close contact with cell wall

Question 18

define plasmolysis

Answer 18

when exosmosis takes place, the cytoplasm shrinks and the plasma mebrane withdraws from the cell wall

Question 19

define deplasmolysis

Answer 19

the recovery or reversal of plasmolysis

Question 20

define flaccidity

Answer 20

condition in which cell wall is shrunken

Question 21

uses of turgidity

Answer 21

1. turgor movement
2. opening and closing of stomata
3. push plant through hard ground
4. builds up root pressure
5. rigidity to soft tissues

Question 22

what is pulvinus?

Answer 22

base of the petioles

Question 23

define root pressure

Answer 23

pressure developed in root due to continuous inward movement of water through cell-to-cell oosmosis which helps in upward ascent of cell sap

Question 24

define guttation

Answer 24

sometimes, root pressure is high enough to force water from the stem all the way to the ends of leaf veins. this excess loss of water is called guttation

Question 26

define capillarity

Answer 26

narrow diameter of xylem vessels promote ascent of sap. narrower the vessel, greater is the ascent of sap exerting a force in it called capillary force