Botany of Transport in plants - Transpiration Short Notes For NEET

Plants absorb water directly from soil through osmosis but indirectly absorbs salt.

Cohesion & adhesion - 130 mts    Transpirational pull- 15 mts/1 hour


Sugar transported in mesophyll cell- companion cell- seive tubes osmotic pressure increases ,,water potential decreases.- from neighbouring xylem vessels by osmosis transferred sugar where by active uploading sucrose..osmotic pressure is less.

In cortex Water move in apoplast (loosely packed).                                  Spherical - more space impervious to water & gases- suberised cell wall& casparian band.

In an endodermal cell without Casparian band apoplast changes to symplast.        In endodermal cell - symplast - pericycle- enters again Apoplast.  chloroplast visible in Hydrilla ( submerged suspended hydrophytes)

Chloroplast largest cell organalle

Size: 2 to 4 micrometer in width     5 to 10 micro

5 to 10 micro meter in length


Prevents rootborne pathogens.Increases absorption of phosphorus from soil.Enables the plant to sustain envorinomental stress. Ensures over all growth of plant.   Pinus seeds do not germinate without mycorrhizae.

Root pressure; observed by Stephen hales

Positive force ascending upwards pushing up droplets of water.    ballon looses water pressure potential is negative.

Money plant- pothos ,,lycopersicon  month - January water excluded tip Cold morning & warm night..-guttation phenomenon.

Loss of water in the form ofwater droplets- guttation.if plant has excess amount of water.pull by transpiration... Push by root pressure.(pull& push both are negative geotrophic)


Morning 6' o clock= evening 6'o clock

Carbon dioxide compensation point.carbon dioxide fixed by photosynthesis= carbon dioxide liberated in respiration.

Cohension - adhesion theory by Dixon.

Attraction between similar water molecules- cohesion.

EXP: Attraction between dissimilar water molecules-Adhesion.

Tensile strength ability to sustain tension.Capillarity- to rise through their columns.


Majotity- stomata,cuticle

Least- cuticle.

Loss of water in the form of vapour from living tissues of aerial parts of plants.

Transpiration plays imp role in SPAC (soil plant atmosphere continuum)

Most of plants- stomata are photo active stomata.but scoto active in succulent plants(cacti, bryophyllum)

Transpiration affected by several external factors-temperature,light, humidity,wind speed,available soil water)

Plant factors- no.& disturbution of stomata, % of opened stomata,water status of the plant,canopy structure, root- shoot ratio ..

Opening & closing of stomata due to turgor changes in guard cells

When guard cells - turgid thin outer walls bulge & force thick inner walls move apart by radial orientation of cellulosemicrofibrils in the cell walls of guard cells.

When guard cells loss turgor because of water stress or water loss elastic inner walls regain theiroriginal position.

Levitt proposed pottassium pump theory .opening & closing of photoactive stomata.


Presence of light pH of guard cells increases due to accumulation of potassium ions from subsidiary cells coupled with active efflux of H + ions ..passive influx of chloride ions.Accumulation of potassium& chloride ions in guard cells decreases  water potential allowing entry of water into guard cells resulting in turgid condition


Turgid guard cells expand outwardly with minute pore centre stomata opens.

At night pottasium & chloride ions move out of guard cells increases water potential in guardcells & exosmosis occur..& become flaccid stomata closes.

In succulent plants  due to accumulation of organic acids in guards cells at night ...water potential gradient established & stomata opens.

Transpiration cools leaf surface (10-15)degrees & maintains shape & structure of plant keeps cell turgid.

Large amount of water recycled from root - leaf- atmoshpere-soil in rain forests.

Makes more humid.

Transpiration considered as necessary evil- beneficial role prevent from causing permanent wilting of plants leading to death.

Carbon dioxide fixation pathway more evolved in C4 plants than C3 plants.

To fix same amount of carbondioxide.C4 plants lose only half as water as C3 plants.