70:(negative vector), while an increase in pressure increases the potential (positive vector). If the flow is not restricted, water will move from an area of higher water potential to an area that is lower potential. A common example is water with dissolved salts, such as seawater or the fluid in a living cell. These solutions have negative water potential, relative to the pure water reference. With no restriction on flow, water will move from the locus of greater potential (pure water) to the locus of lesser (the solution); flow proceeds until the difference in potential is equalized or balanced by another water potential factor, such as pressure or elevation.
615:
756:
is still extremely important in supplying water to plant roots and in engineering applications. The matrix potential is always negative because the water attracted by the soil matrix has an energy state lower than that of pure water. Matrix potential only occurs in unsaturated soil above the water table. If the matrix potential approaches a value of zero, nearly all soil pores are completely filled with water, i.e. fully
696:
the water is lowered. As the concentration of solutes is increased, the osmotic potential of the soil solution is reduced. Since water has a tendency to move toward lower energy levels, water will want to travel toward the zone of higher solute concentrations. Although, liquid water will only move in response to such differences in osmotic potential if a
705:
soluble salts, the osmotic potential is likely to be lower in the soil solution than in the plant root cells. In such cases, the soil solution would severely restrict the rate of water uptake by plants. In salty soils, the osmotic potential of soil water may be so low that the cells in young seedlings start to collapse (
798:
In contrast, atmospheric water potentials are much more negative—a typical value for dry air is −100 MPa, though this value depends on the temperature and the humidity. Root water potential must be more negative than the soil, and the stem water potential must be an intermediate lower value than the
695:
A soil solution also experiences osmotic potential. The osmotic potential is made possible due to the presence of both inorganic and organic solutes in the soil solution. As water molecules increasingly clump around solute ions or molecules, the freedom of movement, and thus the potential energy, of
755:
In many cases, the absolute value of matrix potential can be relatively large in comparison to the other components of water potential discussed above. Matrix potential markedly reduces the energy state of water near particle surfaces. Although water movement due to matrix potential may be slow, it
700:
exists between the zones of high and low osmotic potential. A semipermeable membrane is necessary because it allows water through its membrane while preventing solutes from moving through its membrane. If no membrane is present, movement of the solute, rather than of the water, largely equalizes
704:
Since regions of soil are usually not divided by a semipermeable membrane, the osmotic potential typically has a negligible influence on the mass movement of water in soils. On the other hand, osmotic potential has an extreme influence on the rate of water uptake by plants. If soils are high in
385:
All of these factors are quantified as potential energies per unit volume, and different subsets of these terms may be used for particular applications (e.g., plants or soils). Different conditions are also defined as reference depending on the application: for example, in soils, the reference
69:
Water potential integrates a variety of different potential drivers of water movement, which may operate in the same or different directions. Within complex biological systems, many potential factors may be operating simultaneously. For example, the addition of solutes lowers the potential
795:, at which plant roots cannot extract the water through osmotic diffusion. Soil waterways still evaporate at more negative potentials down to a hygroscopic level, at which soil water is held by solid particles in a thin film by molecular adhesion forces.
177:
791:. Typically, at field capacity, air is in the macropores, and water in the micropores. Field capacity is viewed as the optimal condition for plant growth and microbial activity. At a potential of −1500 kPa, the soil is at its
823:(TDR) can be used to determine soil water potential energy. Tensiometers are limited to 0 to −85 kPa, electrical resistance blocks are limited to −90 to −1500 kPa, neutron probes are limited to 0 to −1500 kPa, and a
634:
than when there is no solute. A solution will have a lower and hence more negative water potential than that of pure water. Furthermore, the more solute molecules present, the more negative the solute potential is.
406:, it increases the total amount of water present inside the cell, which exerts an outward pressure that is opposed by the structural rigidity of the cell wall. By creating this pressure, the plant can maintain
764:. The matrix potential can vary considerably among soils. In the case that water drains into less-moist soil zones of similar porosity, the matrix potential is generally in the range of −10 to −30 kPa.
902:"Gas valves, forests and global change: a commentary on Jarvis (1976) 'The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field'"
875:
748:
within the solid matrix. Force is then required to break these menisci. The magnitude of matrix potential depends on the distances between solid particles—the width of the menisci (also
518:
466:
239:
667:
375:
342:
309:
276:
210:
799:
roots but higher than the leaf water potential, to create a passive flow of water from the soil to the roots, up the stem, to the leaves and then into the atmosphere.
787:, all soil pores are filled with water, and water typically drains from large pores by gravity. At a potential of −33 kPa, or −1/3 bar, (−10 kPa for sand), soil is at
78:
Many different factors may affect the total water potential, and the sum of these potentials determines the overall water potential and the direction of water flow:
681:
environments. In the case of a plant cell, the flow of water out of the cell may eventually cause the plasma membrane to pull away from the cell wall, leading to
609:
585:
561:
541:
468:) of zero, and in this case, solute potential can never be positive. The relationship of solute concentration (in molarity) to solute potential is given by the
84:
740:
can be large and important. The forces between the water molecules and the solid particles in combination with attraction among water molecules promote
30:
per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to
879:
752:
and differing Pa at ends of the capillary)—and the chemical composition of the solid matrix (meniscus, macroscopic motion due to ionic attraction).
957:
Jarvis, P. G. (1976). "The
Interpretation of the Variations in Leaf Water Potential and Stomatal Conductance Found in Canopies in the Field".
827:
is limited to 0 to −10,000 kPa. A scale can be used to estimate water weight (percentage composition) if special equipment is not on hand.
685:. Most plants, however, have the ability to increase solute inside the cell to drive the flow of water into the cell and maintain turgor.
642:. If a living cell is surrounded by a more concentrated solution, the cell will tend to lose water to the more negative water potential (
421:, pressure potential is almost zero. Negative pressure potentials occur when water is pulled through an open system such as a plant
394:
Pressure potential is based on mechanical pressure and is an important component of the total water potential within plant
1011:
62:. Water potential is typically expressed in potential energy per unit volume and very often is represented by the
778:
50:). The concept of water potential has proved useful in understanding and computing water movement within
1030:
478:
808:
1050:
824:
820:
444:
217:
792:
469:
429:) is an important adaptation of the xylem. This tension can be measured empirically using the
761:
697:
645:
410:, which allows the plant to keep its rigidity. Without turgor, plants will lose structure and
353:
320:
287:
254:
188:
1060:
1055:
836:
564:
966:
733:
378:
8:
1065:
841:
689:
970:
934:
901:
594:
588:
570:
546:
526:
1007:
982:
939:
921:
745:
567:, the ratio of amount of particles in solution to amount of formula units dissolved,
618:
The water diffuses across the osmotic membrane to where the water potential is lower
398:. Pressure potential increases as water enters a cell. As water passes through the
172:{\displaystyle \Psi =\Psi _{0}+\Psi _{\pi }+\Psi _{p}+\Psi _{s}+\Psi _{v}+\Psi _{m}}
974:
929:
913:
749:
43:
23:
1003:
Plants and
Microclimate: A Quantitative Approach to Environmental Plant Physiology
1001:
784:
741:
407:
47:
788:
670:
395:
16:
Potential energy of water per unit volume relative to water in known conditions
1044:
986:
925:
816:
757:
678:
430:
403:
978:
943:
917:
63:
706:
682:
418:
674:
959:
Philosophical
Transactions of the Royal Society B: Biological Sciences
906:
Philosophical
Transactions of the Royal Society B: Biological Sciences
639:
627:
425:
vessel. Withstanding negative pressure potentials (frequently called
399:
730:
614:
345:
279:
39:
386:
condition is typically defined as pure water at the soil surface.
631:
411:
312:
246:
35:
31:
812:
623:
417:
The pressure potential in a plant cell is usually positive. In
242:
55:
783:
At a potential of 0 kPa, soil is in a state of saturation. At
441:
Pure water is usually defined as having an osmotic potential (
737:
638:
Osmotic potential has important implications for many living
422:
51:
27:
1031:"Chapter 2. Soil-water Potential: Concepts and Measurement"
726:
722:
718:
669:) of the surrounding environment. This can be the case for
59:
626:
is dissolved in water, water molecules are less likely to
436:
876:"Statkraft to build world's first osmotic power plant"
712:
717:
When water is in contact with solid particles (e.g.,
648:
597:
573:
549:
529:
481:
447:
356:
323:
290:
257:
220:
191:
87:
377:
is the potential due to matrix effects (e.g., fluid
661:
603:
579:
555:
535:
512:
460:
369:
336:
303:
270:
233:
204:
171:
1042:
543:is the concentration in molarity of the solute,
73:
893:
772:
1006:. Cambridge University Press. p. 93.
859:
950:
933:
802:
899:
613:
1043:
956:
864:(Fourth ed.). Sinauer Associates.
999:
767:
389:
688:This effect can be used to power an
437:Osmotic potential (solute potential)
713:Matrix potential (Matric potential)
13:
673:organisms living in sea water and
650:
513:{\displaystyle \Psi _{\pi }=-MiRT}
483:
449:
358:
325:
292:
259:
222:
193:
160:
147:
134:
121:
108:
95:
88:
14:
1077:
1023:
1000:Jones, Hamlyn G. (2013-12-12).
779:Soil-plant-atmosphere continuum
993:
868:
853:
1:
611:is the absolute temperature.
74:Components of water potential
461:{\displaystyle \Psi _{\pi }}
234:{\displaystyle \Psi _{\pi }}
212:is the reference correction,
7:
830:
42:and matrix effects such as
10:
1082:
776:
736:between the water and the
821:time-domain reflectometry
662:{\displaystyle \Psi _{w}}
370:{\displaystyle \Psi _{m}}
337:{\displaystyle \Psi _{v}}
304:{\displaystyle \Psi _{s}}
271:{\displaystyle \Psi _{p}}
205:{\displaystyle \Psi _{0}}
900:Beerling, D. J. (2015).
847:
811:, electrical resistance
773:Soil-plant-air continuum
344:is the potential due to
793:permanent wilting point
979:10.1098/rstb.1976.0035
918:10.1098/rstb.2014.0311
803:Measurement techniques
698:semipermeable membrane
663:
619:
605:
581:
557:
537:
514:
462:
371:
338:
305:
272:
235:
206:
173:
860:Taiz; Zeiger (2002).
837:Water retention curve
744:and the formation of
734:intermolecular forces
664:
617:
606:
582:
558:
538:
515:
463:
381:and surface tension.)
372:
339:
306:
273:
236:
207:
174:
646:
622:For example, when a
595:
571:
547:
527:
479:
470:van 't Hoff equation
445:
354:
321:
288:
255:
218:
189:
85:
46:(which is caused by
971:1976RSPTB.273..593J
842:Pore water pressure
690:osmotic power plant
912:(1666): 20140311.
768:Empirical examples
762:retentive capacity
677:plants growing in
659:
620:
601:
589:ideal gas constant
577:
565:van 't Hoff factor
553:
533:
510:
458:
390:Pressure potential
367:
334:
301:
268:
231:
202:
169:
725:particles within
604:{\displaystyle T}
580:{\displaystyle R}
556:{\displaystyle i}
536:{\displaystyle M}
419:plasmolysed cells
1073:
1051:Plant physiology
1037:
1035:
1018:
1017:
997:
991:
990:
965:(927): 593–610.
954:
948:
947:
937:
897:
891:
890:
888:
887:
878:. Archived from
872:
866:
865:
862:Plant Physiology
857:
750:capillary action
701:concentrations.
668:
666:
665:
660:
658:
657:
610:
608:
607:
602:
586:
584:
583:
578:
562:
560:
559:
554:
542:
540:
539:
534:
519:
517:
516:
511:
491:
490:
467:
465:
464:
459:
457:
456:
376:
374:
373:
368:
366:
365:
343:
341:
340:
335:
333:
332:
310:
308:
307:
302:
300:
299:
277:
275:
274:
269:
267:
266:
240:
238:
237:
232:
230:
229:
211:
209:
208:
203:
201:
200:
178:
176:
175:
170:
168:
167:
155:
154:
142:
141:
129:
128:
116:
115:
103:
102:
44:capillary action
24:potential energy
1081:
1080:
1076:
1075:
1074:
1072:
1071:
1070:
1041:
1040:
1033:
1029:
1026:
1021:
1014:
998:
994:
955:
951:
898:
894:
885:
883:
874:
873:
869:
858:
854:
850:
833:
805:
781:
775:
770:
760:and at maximum
742:surface tension
715:
653:
649:
647:
644:
643:
596:
593:
592:
572:
569:
568:
548:
545:
544:
528:
525:
524:
486:
482:
480:
477:
476:
452:
448:
446:
443:
442:
439:
392:
361:
357:
355:
352:
351:
328:
324:
322:
319:
318:
295:
291:
289:
286:
285:
262:
258:
256:
253:
252:
225:
221:
219:
216:
215:
196:
192:
190:
187:
186:
163:
159:
150:
146:
137:
133:
124:
120:
111:
107:
98:
94:
86:
83:
82:
76:
48:surface tension
20:Water potential
17:
12:
11:
5:
1079:
1069:
1068:
1063:
1058:
1053:
1039:
1038:
1025:
1024:External links
1022:
1020:
1019:
1012:
992:
949:
892:
867:
851:
849:
846:
845:
844:
839:
832:
829:
817:neutron probes
804:
801:
789:field capacity
777:Main article:
774:
771:
769:
766:
714:
711:
656:
652:
600:
576:
552:
532:
521:
520:
509:
506:
503:
500:
497:
494:
489:
485:
455:
451:
438:
435:
391:
388:
383:
382:
364:
360:
349:
331:
327:
316:
298:
294:
283:
265:
261:
250:
228:
224:
213:
199:
195:
180:
179:
166:
162:
158:
153:
149:
145:
140:
136:
132:
127:
123:
119:
114:
110:
106:
101:
97:
93:
90:
75:
72:
64:Greek letter ψ
15:
9:
6:
4:
3:
2:
1078:
1067:
1064:
1062:
1059:
1057:
1054:
1052:
1049:
1048:
1046:
1032:
1028:
1027:
1015:
1013:9781107511637
1009:
1005:
1004:
996:
988:
984:
980:
976:
972:
968:
964:
960:
953:
945:
941:
936:
931:
927:
923:
919:
915:
911:
907:
903:
896:
882:on 2009-02-27
881:
877:
871:
863:
856:
852:
843:
840:
838:
835:
834:
828:
826:
822:
818:
814:
810:
800:
796:
794:
790:
786:
780:
765:
763:
759:
753:
751:
747:
743:
739:
735:
732:
728:
724:
720:
710:
708:
702:
699:
693:
691:
686:
684:
680:
676:
672:
654:
641:
636:
633:
629:
625:
616:
612:
598:
590:
574:
566:
550:
530:
507:
504:
501:
498:
495:
492:
487:
475:
474:
473:
471:
453:
434:
432:
431:Pressure bomb
428:
424:
420:
415:
413:
409:
405:
404:cell membrane
401:
397:
387:
380:
362:
350:
347:
329:
317:
314:
296:
284:
281:
263:
251:
248:
244:
226:
214:
197:
185:
184:
183:
164:
156:
151:
143:
138:
130:
125:
117:
112:
104:
99:
91:
81:
80:
79:
71:
67:
65:
61:
57:
53:
49:
45:
41:
38:, mechanical
37:
33:
29:
25:
21:
1061:Soil physics
1056:Hydrostatics
1002:
995:
962:
958:
952:
909:
905:
895:
884:. Retrieved
880:the original
870:
861:
855:
806:
797:
782:
754:
716:
703:
694:
687:
637:
621:
522:
440:
426:
416:
393:
384:
181:
77:
68:
19:
18:
809:tensiometer
683:plasmolysis
313:gravimetric
1066:Potentials
1045:Categories
886:2014-01-29
785:saturation
707:plasmolyze
675:halophytic
315:component,
282:component,
249:potential,
987:0962-8436
926:0962-8436
758:saturated
651:Ψ
640:organisms
630:away via
496:−
488:π
484:Ψ
454:π
450:Ψ
400:cell wall
359:Ψ
326:Ψ
293:Ψ
260:Ψ
227:π
223:Ψ
194:Ψ
161:Ψ
148:Ψ
135:Ψ
122:Ψ
113:π
109:Ψ
96:Ψ
89:Ψ
944:25750234
831:See also
731:adhesive
379:cohesion
346:humidity
280:pressure
40:pressure
967:Bibcode
935:4360119
815:block,
746:menisci
632:osmosis
628:diffuse
587:is the
563:is the
427:tension
311:is the
278:is the
247:osmotic
241:is the
182:where:
56:animals
36:gravity
32:osmosis
22:is the
1010:
985:
942:
932:
924:
813:gypsum
679:saline
671:marine
624:solute
591:, and
523:where
408:turgor
243:solute
58:, and
52:plants
1034:(PDF)
848:Notes
819:, or
738:solid
423:xylem
396:cells
348:, and
28:water
1008:ISBN
983:ISSN
940:PMID
922:ISSN
727:soil
723:sand
719:clay
412:wilt
402:and
60:soil
975:doi
963:273
930:PMC
914:doi
910:370
825:TDR
729:),
721:or
709:).
245:or
26:of
1047::
981:.
973:.
961:.
938:.
928:.
920:.
908:.
904:.
807:A
692:.
472::
433:.
414:.
66:.
54:,
34:,
1036:.
1016:.
989:.
977::
969::
946:.
916::
889:.
655:w
599:T
575:R
551:i
531:M
508:T
505:R
502:i
499:M
493:=
363:m
330:v
297:s
264:p
198:0
165:m
157:+
152:v
144:+
139:s
131:+
126:p
118:+
105:+
100:0
92:=
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
