Editing Hygroscopy (section)

===Hygroscopic-assisted propagation examples===
Typical of hygroscopic movement are plant tissues with "closely packed long (columnar) parallel thick-walled cells (that) respond by expanding longitudinally when exposed to humidity and shrinking when dried (Reyssat et al., 2009)".<ref name="Reyssat" /> Cell orientation, pattern structure (annular, planar, bi-layered or tri-layered) and the effects of the opposite-surface's cell orientation control the hygroscopic reaction. Moisture responsive seed encapsulations rely on valves opening when exposed to wetting or drying; discontinuous tissue structures provide such predetermined breaking points (sutures), often implemented via reduced cell wall thickness or seams within bi- or tri-layered structures.<ref name="Huss" /> Graded distributions varying in density and/or cell orientation focus hygroscopic movement, frequently observed as biological actuators (a hinge function); e.g. pinecones (''Pinus spp.''), the ice plant (''Aizoaceae spp.'') and the wheat awn (''Triticum spp.''),<ref name="Brulé">{{cite journal |last1=Brulé |first1=Véronique |last2=Rafsanjani |first2=Ahmad |last3=Asgari |first3=Meisam |last4=Western |first4=Tamara L. |last5=Pasini |first5=Damiano |title=Three-dimensional functional gradients direct stem curling in the resurrection plant Selaginella lepidophylla |journal=Journal of the Royal Society Interface |date=October 2019 |volume=16 |issue=159 |doi=10.1098/rsif.2019.0454 |pmid=31662070 |pmc=6833318 }}</ref> described below.

[[File:Favourite flowers of garden and greenhouse (10574920866).jpg|thumb|Illustration botanique, ''Xerochrysum (Helichrysum) bracteatum''; No.1- Capitulum [bracts, florets, stamens]]]
* Hygroscopic bi-layered cell arrays act as a [[Pseudanthium|capitulum]] hinge in some plants, ''[[Xerochrysum bracteatum]]'' and ''[[Comanthera elegans|Syngonanthus elegans]]'' being examples. The hygroscopic bending of involucral bracts surrounding a capitulum contributes to flower protection and pollination<ref name="Borowska-Wykręt" /> and assists dispersion by protecting delicate pappi filaments from entanglement or destruction by precipitation,<ref name="Sheldon">{{cite journal |last1=Sheldon |first1=J. C. |last2=Burrows |first2=F. M. |title=The Dispersal Effectiveness of the Achene-Pappus Units of Selected Compositae in Steady Winds with Convection |journal=New Phytologist |date=May 1973 |volume=72 |issue=3 |page=666 |doi=10.1111/j.1469-8137.1973.tb04415.x |doi-access=free |bibcode=1973NewPh..72..665S }}</ref> e.g. ''[[Taraxacum]]'' (dandelions). In nature these [[Bract#Involucral bracts|involucral bracts]] have a [[Circadian rhythm#In plants|diurnal rhythm]]. The [[Whorl (botany)|whorl]] of hygroscopic bracts bend outward exposing the [[Pseudanthium|capitulum (see illustration)]] during the day, then inward, closing it at night, as the relative humidity shifts in response to the daily temperature change. [[Glossary of botanical terms#scarious|Bracts are scarious]], the hinge and blade composed exclusively of dead cells (Nishikawa et al., 2008), allowing the hygroscopically activated bracts to function from flowering through achene dispersal.<ref name="Borowska-Wykręt" /> Physiologically, the bract's lower section is source to the hinge-like function, consisting of sclerenchyma-like [[Leaf#Epidermis|abaxial]] (inner petal) tissue, parenchyma and adaxial epidermis (outer petal tissue).<ref name="Borowska-Wykręt">{{cite journal |last1=Borowska-Wykręt |first1=Dorota |last2=Rypień |first2=Aleksandra |last3=Dulski |first3=Mateusz |last4=Grelowski |first4=Michał |last5=Wrzalik |first5=Roman |last6=Kwiatkowska |first6=Dorota |title=Gradient of structural traits drives hygroscopic movements of scarious bracts surrounding Helichrysum bracteatum capitulum |journal=Annals of Botany |date=June 2017 |volume=119 |issue=8 |pages=1365–1383 |doi=10.1093/aob/mcx015 |pmid=28334385 |url=https://academic.oup.com/aob/article/119/8/1365/3073703 |access-date=12 February 2023|pmc=5604587 }}</ref> Bract cell wall composition is rather uniform but its cells gradually change in orientation. The bract's hygroscopic bending is due to the differing cell orientations of its inner and outer epidermides, causing adaxial–abaxial force gradients between opposing sides that change with moisture; thus, the aggregate hygrometric force, in whorl unison, controls the capitulum's repetitive opening and closing.  
*Some trees and shrubs in fire-prone regions evolved a dual-stage hygroscopic dispersal; an initial thermo-sensitive enabling (extreme heat or fire), then a [[Serotiny|serotinous]] hygroresponsive seed release. Examples are the woody fruits of [[Myrtaceae]] (e.g. ''[[Eucalyptus]] species plurimae, [[Melaleuca]] spp.'') and [[Proteaceae]] (e.g. ''[[Hakea]] spp., [[Banksia]] spp., [[Xylomelum]] spp.'') and the woody cones of ''[[Pinaceae]]'' (e.g. ''[[Pine|Pinus spp.]]'') and the cypress family (''[[Cupressaceae]]''), e.g. the giant sequoia (''[[Sequoiadendron giganteum]]'')).<ref name="Huss" /><ref name="HussT" /> Typical in lodgepole pine (''[[Pinus contorta]]''), ''Eucalyptus'', and ''Banksia'' are resin-sealed seed encapsulations that require the heat of fire to physically melt the resin, [[Serotiny#Fire-mediated serotiny|enabling serotinous seed release]].<ref name="Petruzzello">{{cite web |last1=Petruzzello |first1=Melissa |title=Playing with Wildfire: 5 Amazing Adaptations of Pyrophytic Plants |url=https://www.britannica.com/list/5-amazing-adaptations-of-pyrophytic-plants |website=britannica.com |publisher=Encyclopædia Britannica, Inc. |access-date=22 February 2023 |date=2023}}</ref> Such seed encapsulations may "reduce seed loss or damage from [[Seed predation|granivores]], desiccation, and fire (Moya et al., 2008; Talluto & Benkman, 2014; Lamont et al., 2016, 2020)."<ref name="Huss" /> The similarity of dual-stage dispersal techniques between different clades, [[Flowering plant|angiosperms]] and [[gymnosperms]], can be interpreted as a result of [[Convergent evolution#In plants|convergent evolution]] (e.g. Clarke et al., 2013).<ref name="Huss" />[[File:2018-01-31 171405 Banksia Attenuata, Nambung National Park, West Australia anagoria.JPG|thumb|''Banksia Attenuata'' cone with open follicles]]
**''[[Banksia attenuata]]'', typical of ''[[Banksia#Description|Banksia spp.]]'', has a seed bearing [[Follicle (fruit)|follicle]] composed of a bi-layer hygroscopic cell network. The  woody follicle is thermo-sensitive, then hygroresponsive; serotinous humidity opening the ventral suture and exposing seed when germination conditions are favorable.<ref name="HussT" /> Physiologically, the heat-sensitive follicle valves of ''Banksia spp.'' are sealed by a wax (resin) layer, released by high ambient temperatures (fire), "thereby facilitating opening (e.g. Huss et al., 2018)."<ref name="Huss" /> The follicle mesocarp consists of high density branched fiber bundles; the endocarp, low density parallel fibers. A suture is caused by differential hygroscopic movements between layers, their microfibril structures having a large angle disparity (microfibril angle (MFA) γ = 75–90°).<ref name="Huss" />
**Pine cone scales (''[[Pine|pinaceae spp.]]'') employ a hygromorphic hinge for their seed release. Physiology involves a bi-layered structure of closely packed long parallel thick-walled cells. Fiber alignments within layers are non-uniform, varying longitudinally, producing different microfibril angles (MFAs) of 30° and 74° between layers over the span of the scale.<ref name="HussT" /> The region of greatest MFA, the hinge knuckle, is a small region near the scale and midrib (central stem) union.<ref name="Reyssat" /> In mature pine cones the outer scale layer is the controlling tissue, its long thick-walled cells responding longitudinally to environmental humidity. Distortion occurs in the knuckle region as movement of the outer layer overtakes that of the more passive inner scale layer, forcing the scale to bend or flex.  The remainder of the scale is hygroscopically passive, though amplifies apex displacement via length and geometrically;<ref name="Reyssat" /> e.g. bending the scale closed with hydration or flexing it open with dehydration- releasing seed.[[File:Taraxacum officinale kz05.jpg|thumb|''Taraxacum officinale'' capitulum and achene [seed-beak-apical plate-pappus]]]
* Flowering plants of the ''[[Asteraceae]]'' family have hygroscopically-influenced dispersion, coordinating [[Seed dispersal#Allochory|anemochory (wind dispersal)]] with favorable environmental conditions,<ref name="Seale" /> common in ''A.'' genera ''[[Erigeron]], [[Leontodon]], [[Senecio]], [[Sonchus]]'' and ''[[Taraxacum]]''.<ref name="Eastman">{{cite web |last1=Eastman |first1=John |title=Seeds that plant themselves |url=https://www.indefenseofplants.com/blog/2015/2/18/seeds-that-plant-themselves |website=indefenseofplants.com |access-date=1 March 2023 |date=February 18, 2015}}</ref> As example, the flight-enabling [[Pappus (botany)|pappus]] of the common [[Taraxacum|dandelion]] [[achene]] undergoes binary morphing (opened or closed) of its whisker-like filaments, in unison with chorused responses of the remaining achenes. Pappus movement is controlled via a hygroscopic actuator in the apical plate, at the beak's top, the locus for all the achene's filaments.  High humidity causes each pappus to close, contracting its radially patterned structure, reducing its area and the likelihood of wind current dispersal.<ref name="Seale" /> For any achene that become released, flight dynamics of the reduced pappus dramatically limit dispersal range.<ref name="Seale">{{cite journal |last1=Seale |first1=Madeleine |last2=Kiss |first2=Annamaria |last3=Bovio |first3=Simone |last4=Viola |first4=Ignazio Maria |last5=Mastropaolo |first5=Enrico |last6=Boudaoud |first6=Arezki |last7=Nakayama |first7=Naomi |title=Dandelion pappus morphing is actuated by radially patterned material swelling |journal=Nature Communications |date=May 6, 2022 |volume=13 |issue=2498 (2022) |page=2498 |doi=10.1038/s41467-022-30245-3 |pmid=35523798 |pmc=9076835 |bibcode=2022NatCo..13.2498S |hdl=20.500.11820/b89b6b81-c97c-4145-a0a7-253119cd0c66 |hdl-access=free }}</ref> The hygroscopic actuator's responsiveness to changes in relative humidity (RH) is predictable, repeatable; e.g. the pappi of ''[[Centaurea|centaurea imperialis]]'' remain closed at ≥ 78% RH and open completely at ≤ 75% RH.<ref name="Sheldon" /> During more favorable lower humidity conditions, pappi fully expand and wind current allochory is re-enabled. [[File:Bauhinia variegata MHNT.BOT.2011.3.22.jpg|thumb|Orchid tree (''[[Bauhinia variegata]]'') seed pods]]
*The orchid tree (''[[Bauhinia variegata]]'') depends upon hygro-responsive twisting for its dispersal.  Its seed pod contains two hygroscopic [[Ground tissue#sclerenchyma|sclerenchyma]] fibre layers, nearly orthogonal, joining at the valves. During [[dehiscence (botany)|dehiscence]] the large 90° microfibril angle between [[Fruit anatomy#endocarp|endocarp]] layers,<ref name="HussT">{{cite journal |last1=Huss |first1=Jessica C. |last2=Gierlinger |first2=Notburga |title=Functional packaging of seeds |journal=New Phytologist: International Journal of Plant Science |date=June 2021 |volume=230 |issue=6 |pages=Table 1 |doi=10.1111/nph.17299 |pmid=33629369 |pmc=8252473 |bibcode=2021NewPh.230.2154H }}</ref> combined with dual sided shrinkage, results in opposing helical torques<ref name="Huss" /> that force a suture at the weakest point, the seed case valves; their opening releases seed.<ref name="Borowska-Wykręt" />[[File:Ruschia sp. (Aizoaceae) (36689680823).jpg|thumb|''[[Ruschia|Ruschia sp.]]'' (''Aizoaceae'') flowers and multi-stage seed capsules]]
*Some plants synchronize the opening of their mature seed capsule with active rainfall- hygrochasy. This dispersal technique is frequently observed in the arid regions of southern and eastern Africa, the Israeli desert, parts of North America and Somalia, and believed evolved to offer higher survival rates in arid environs.<ref name="Pufal">{{cite journal |last1=Pufal |first1=Gesine |last2=Garnock-Jones |first2=Phil |title=Hygrochastic capsule dehiscence supports safe site strategies in New Zealand alpine Veronica (Plantaginaceae) |journal=Annals of Botany |date=September 2010 |volume=106 |issue=3 |pages=405–412 |doi=10.1093/aob/mcq136 |pmid=20587583 |pmc=2924830 }}</ref> Hygrochasy is commonly associated with family ''[[Aizoaceae]] spp.'', the ice plant, as > 98% of its species utilize post-wetting [[Dehiscence (botany)#Fruit dehiscence|dehiscence]]; such dispersal is also observed in family ''[[Plantaginaceae]]'' with the alpine [[Veronica (plant)|Veronica]] of New Zealand, evolving in the last 9Myr.<ref name="Pufal" /> Common to all seed capsules are triangular circumferentially-arranged hygroscopic keels (valves) covering its seeds. These protective valves mechanically open only when hydrated with liquid water.<ref name="Harrington">{{cite journal |last1=Harrington |first1=Matthew J. |last2=Razghandi |first2=Khashayar |last3=Ditsch |first3=Friedrich |last4=Guiducci |first4=Lorenzo |last5=Rueggeberg |first5=Markus |last6=Dunlop |first6=John W.C. |last7=Fratzl |first7=Peter |last8=Neinhuis |first8=Christoph |last9=Burgert |first9=Ingo |title=Origami-like unfolding of hydro-actuated ice plant seed capsules |journal=Nature Communications |date=7 June 2011 |volume=2 |issue=337 (2011) |page=337 |doi=10.1038/ncomms1336 |pmid=21654637 |bibcode=2011NatCo...2..337H |doi-access=free }}</ref> Each keel (five for ''[[Delosperma|Delosperma nakurense (Engl.) Herre]]'') is composed of cellulosic lattice tissue that swells with hydration, opening within minutes.  The enlarged cells force straightening of an inherent desiccated fold in the keel, the hygroscopic hinge, near the keel's union with the capsule perimeter. Fully opened, the keel pivots over 150°,<ref name="Harrington" /> upward then backward, exposing seed compartments, one beneath each valve, separated by [[Septum#Botany|septa]], all resting upon the capsule floor. Seeds are visible, but restrained by the cup-like ring created by the encircling keels. The final requirement for dispersal is rainfall, or sufficient moisture, to flush seed from this barrier, colloquially termed the splash cup.<ref name="Pufal" /> Seed that overflows or splashes from the cup is dispersed to the nearby ground. Any  remaining seed will be preserved when keels desiccate, hygroscopically shrink, and restore to their natural folded, closed state. The hygromorphic process is reversible, repeatable; neglected seed having subsequent dispersal opportunity via future rainfalls.[[File:Erodium cicutarium MHNT.jpg|thumb|Common stork's-bill (''[[Erodium cicutarium]]'') achenes with coiled awns]][[File:2015.06.27 11.30.41 IMG 2780 - Flickr - andrey zharkikh.jpg|thumb|Needle-and Thread (''[[Hesperostipa comata]]'') seedbuds]]
*The seeds of some flowering herbs and grasses have [[awn (botany)|hygroscopic appendages (awns)]] that bend with changes in humidity, enabling them to disperse over the ground, termed [[Dispersal vector#Self-generated dispersal|herpochory]]. The awn will thrust (or twist) when the seed is released, its motion dependent upon plant physiology. Subsequent hygrometric changes cause movements to repeat, thrusting (or twisting), pushing the seed into the ground.<ref name="Brulé" />

Two ''angiospermae'' families have similar methods of dispersal, though method of implementation varies within family: ''Geraniaceae'' family examples are the common stork's-bill (''[[Erodium cicutarium]]'') and  geraniums (''Pelargonium sp.''); ''Poaceae'' family, Needle-and-Thread (''[[Hesperostipa comata]]'') and wheat (''[[Triticum spp.]]''). All rely upon a bi-layered parallel fiber hygroscopic cell physiology to control the awn's movement for dispersal and self-burial of seeds.<ref name="Huss" /> Alignment of cellulose fibrils in the awn's controlling cell wall determines direction of movement. If fiber alignments are tilted, non-parallel venation, a helix develops and awn movement becomes twisting (coiling) instead of bending;<ref name="Borowska-Wykręt" /> e.g. coiling occurs in awns of ''Erodium'',<ref name="Huss" /> and ''Hesperostipa''.<ref>[https://www.fs.fed.us/database/feis/plants/graminoid/hescom/all.html Fire Effects Information System, Species: ''Hesperostipa comata''] {{Webarchive|url=https://web.archive.org/web/20170528221746/https://www.fs.fed.us/database/feis/plants/graminoid/hescom/all.html |date=2017-05-28 }} [[United States Forest Service|U.S. Department of Agriculture Forest Service]]</ref>
*Some plants use hygroscopic movements for [[Seed dispersal#Ballistic dispersal|Ballochory]] (self-dispersal), active ballists forcibly ejecting their seeds; e.g. species of geranium, violet, wood sorrel, witch hazel, touch-me-not (Impatiens), and acanthus. Rupturing of the ''[[Bauhinia purpurea]]'' seed pod reportedly propels its seed up to 15 metres distance.<ref name="Britannica">{{cite web |title=Seed-Plant-Reproductive-Part: Dispersal by water |url=https://www.britannica.com/science/seed-plant-reproductive-part/Dispersal-by-water |website=www.britannica.com |publisher=Britannica |access-date=5 March 2023 |pages=Seed: Self-dispersal |date=2023}}</ref>