Measurements Turgor pressure

1 measurements

1.1 units
1.2 methods

1.2.1 water potential equation
1.2.2 pressure-bomb technique
1.2.3 atomic force microscope
1.2.4 pressure probe

1.2.4.1 micro-manipulation probe

measurements

when measuring turgor pressure in plants, many things have taken account. stated turgid cells have turgor pressure value equal of cell, , flaccid cells have value @ or near zero. other cellular mechanisms taken consideration include protoplast, solutes within protoplast (solute potential), transpiration rates of plant, , tension of cell walls. measurement limited depending on method used, of explored , explained below. not methods can used organisms, due size , other properties. example, diatom won t have same properties plant, place constrictions on used infer turgor pressure.

units

units used measure turgor pressure independent measures used infer values. common units include bars, mpa, or newtons. 1 bar equal .1 mpa.

methods
water potential equation

turgor pressure can deduced when total water potential, Ψw, , osmotic potential, Ψs, known in water potential equation. these equations used measure total water potential of plant using variables such matric potential, osmotic potential, pressure potential, gravitational effects , turgor pressure. after taking difference between Ψs , Ψw, value turgor pressure given. when using method, gravity , matric potential considered negligible, since values either negative or close zero.

pressure-bomb technique

diagram of pressure bomb

the pressure bomb developed plant physiologist lan wang , colleagues in order test water movement through plants. instrument used measure turgor pressure placing leaf (with stem attached) closed chamber pressurized gas added in increments. measurements taken when xylem sap appears out of cut surface , @ point doesn t accumulae or retreat cut surface.

atomic force microscope

atomic force microscopes use type of scanning probe microscopy (spm). small probes introduced area of interest, , spring within probe measures values via displacement. method can used measure turgor pressure of organisms. when using method, supplemental information such continuum mechanic equations, single force depth curves , cell geometries can used quantify turgor pressures within given area (usually cell).

pressure probe

this machine used measure individual algal cells, can used on larger-celled specimens. used on higher plant tissues, wasn t used measure turgor pressure until hüsken , zimmerman improved on method. pressure probes measure turgor pressure via displacement. glass micro-capillary tube inserted cell , whatever cell exudes tube observed through microscope. attached device measures how pressure required push emission cell.

micro-manipulation probe

these used accurately quantify measurements of smaller cells. in experiment weber, smith , colleagues, single tomato cells compressed between micro-manipulation probe , glass allow pressure probe s micro-capillary find cell s turgor pressure.