Transport in Plants/पादपों में परिवहन

             Transport in Plants 

Introduction –

Father of plant physiology – Stephan Hales

Father of Indian plant physiology – J.C. Bose

What is translocation?

              For smaller distances nutrients are translocated by diffusion, active transport and for larger distances nutrients are translocated by xylem or phloem, It is called translocation/transport in plants.

Direction of transport –

                                          Water and nutrients are translocated from root to stem by xylem – unidirectional transportation.

Organic substances/compounds which synthesized in leaved by photosynthesis translocated to plant’s other parts by phloem – multidirectional transportation.

*Transportation of Hormones/plant growth factors is unidirectional.

Types of transportation –

1.Simple diffusion -  transport from high concentration to low concentration. Pressure of diffused molecules on medium is called diffusion pressure.

2.Facilitated diffusion – transport by specific motor proteins or channel proteins are called facilitated diffusion. It is divided in 3 types –

I.Uniport – when a molecule’s transport doesn’t affect other molecule’s transport. Na⁺, K⁺, H⁺ pump

II.Symport – Na⁺ Cl^- pump

III.Antiport – Na⁺ K⁺ pump

                                                                                                                                                                                           

3.Osmosis – Transportation from lower concentration to higher concentration by half transparent membrane. Discovered by Abbe Nollet. Osmosis pressure is a pressure which stops solvents movement when it pressurized against solvents direction.

4.Active transport – transport from lower concentration to higher concentration, in this process energy consumed by plant. It is also called uphill transport.

5.Inactive transport – transport from higher to lower concentration. Simple diffusion, facilitated diffusion and osmosis are types of inactive transport.

Water absorption –

Maximum water absorption – by root hair region or mature region

Path of water absorption –

Soil water – Epiblema – Cortex – Passage cells of Endodermis – Pericycle – Protoxylem – Metaxylem

There are three types of path of water absorption –

1.Apoplast – in this type of path water goes through non-living structures such as – cell wall, xylem cavity, intercellular gaps. It is directed by diffusion. There is no need of energy.

2.Symplast – in this type of path water goes through plasmodesmata from one cell to another. It is based on osmosis and there is need of energy.

3.Vacuolar – in this type of path water goes through plasma membrane from one cell to another cell. It is also based on osmosis and it also requires energy.

Apoplast and Symplast word is given by Munch.

Food transport in plants –

food and organic substances transported by phloem – proved by girdling experiment. Food transportation done between source and sink.

Photosynthetic leaves – source

       Other plant body parts – sink

Food transportation is a multidirectional process, whenever water transportation is a unidirectional process. Food transportation is done in form of sucrose.