Cambial responsiveness in four eucalypt varieties to onset of drought as well as spring conditions

Simple item page
dc.contributor.advisorDrew, David Michaelen_ZA
dc.contributor.advisorEckert, Michelleen_ZA
dc.contributor.authorNevhungwili, Mashudu Lucyen_ZA
dc.contributor.otherStellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.en_ZA
dc.date.accessioned2024-02-27T12:22:32Zen_ZA
dc.date.accessioned2024-04-26T14:29:05Zen_ZA
dc.date.available2024-02-27T12:22:32Zen_ZA
dc.date.available2024-04-26T14:29:05Zen_ZA
dc.date.issued2024-02en_ZA
dc.descriptionThesis (MSc)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT:Xylogenesis is a highly dynamic and seasonal process resulting from variations in cell production by the meristem (vascular cambium). This process results in the formation of secondary xylem and phloem cells within the period of active wood formation, leading to increased stem radius. This study explored secondary wood formation amongst four Eucalyptus varieties (Eucalyptus grandis, Eucalyptus grandis x nitens, Eucalyptus grandis x urophylla and Eucalyptus urophylla)in response to change in environmental conditions. It focussed on two study periods (an induced drought and spring period)in order to see how sensitive the varieties are to drought along with the responsiveness of the varieties to change in growth conditions during spring. To answer these questions, two-year old trees growing in an uncontrolled environment with Mediterranean climate were monitored during drought induced (March) and spring growth (August-September) seasons of 2022. Repeated wood core sampling, together with diameter change measurements, were carried out twice a week during drought induced period and once a week during spring period. Environmental data was obtained from a weather station placed adjacent to the trees. From the selected trees wood samples were extracted using a Trephor corer in a descending spiral pattern. Microcores were cut, stained, and fixed in the laboratory to produce anatomical sections, which were then observed under both Brightfield and Fluorescence microscopic imagery. The developing zone width (cambial and expanding cells zone) along with the cells in two stages of xylogenesis (cell division and differentiation) were analysed using QuPath. The results of the drought induced period showed that irrigation suspension had the greatest effect on wood formation in all studied varieties. Trees experiencing stress showed a decreased cell production as drought progressed, indicating ceased cambial activity, resulting to narrower developing zone contributing to a decreased tree size. After temporal irrigation during this period, varieties showed recovery which was observed in both stem radius and cell production. The response in the developing zone was however delayed in Eucalyptus grandis x urophylla and Eucalyptus urophylla. The response to irrigation application showed that the cambium of trees was in an eco-dormancy stage before irrigation application. The results on irrigated trees during spring period showed an active cambium during late-winter to early spring with no spring start up evident. Rainfall during this season did not show noticeable effects on wood formation across all varieties. The response of the varieties showed different maximum temperatures for wood formation during spring period. Eucalyptus urophylla showed to be sensitive to daily temperatures of above 16°C, while other varieties were sensitive to temperatures above 17°C. Results from this study lead to the conclusion that secondary wood formation in Eucalyptus varieties growing in the Mediterranean climate is controlled by how favorable the environment is.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Xylogenese is 'n hoogs dinamiese en seisoenale proses wat spruit vanuit variasies in selproduksie deur die meristeem (vaskulêre kambium). Hierdie proses lei tot die vorming van sekondêre xileem- en floëemselle binne die tydperk van aktiewe houtvorming, wat lei tot verhoogde stamdikte. Hierdie studie het sekondêre houtvorming onder vier Eucalyptus-variëteite (Eucalyptus grandis, Eucalyptus grandis x nitens, Eucalyptus grandis x urophylla en Eucalyptus urophylla) in reaksie tot die verandering in omgewingstoestande ondersoek. Daar was gefokus op twee studieperiodes ('n geïnduseerde droogte en lenteperiode) om te sien hoe sensitief die variëteite vir droogte is, asook om te bepaal hoe die variëteite reageer op verandering in groeitoestande gedurende die lente. Om hierdie vrae te beantwoord, is tweejarige bome wat in 'n onbeheerde omgewing met ʼn Mediterreense klimaat gegroei het gemonitor tydens droogte-geïnduseerde (Maart) en lentegroei (Augustus-September) seisoene van 2022. Herhaalde houtkernmonsters, tesame met metings van deursneeverandering, is twee keer per week tydens die droogte-geïnduseerde periode en een keer per week gedurende die lente-periode uitgevoer. Omgewingsdata is verkry vanaf 'n weerstasie wat langs die bome geplaas was. Van die geselekteerde bome is houtmonsters onttrek met behulp van 'n Trephor-kerner in 'n dalende spiraalpatroon. Mikrokerne is gesny, gekleur en gemonteer in die laboratorium om anatomiese snitte te produseer, wat dan onder beide lig en fluoressensie mikroskopie waargeneem en gefotografeer was. Die ontwikkelende sone se wydte (kambiale sone en sone van vergroting van selle) asook die selle wat in twee stadiums van xylogenese was (seldeling en differensiasie) was met behulp van QuPath ontleed. Die resultate van die droogte-geïnduseerde tydperk het getoon dat staking van besproeiing die grootste effek op houtvorming in alle bestudeerde variëteite gehad het. Bome wat stres ervaar het, het 'n verlaagte selproduksie getoon soos droogte gevorder het, wat opgestaakte kambiale aktiwiteit aandui, wat gelei het tot ʼn nouer ontwikkelende sone wat bygedra het tot verminderde boomgrootte. Na tydelike besproeiing plaasgevind het gedurende hierdie tydperk, het variëteite herstel getoon wat in beide stamradius en selproduksie waargeneem is. Die reaksie in die ontwikkelende sone was egter vertraag in Eucalyptus grandis x urophylla en Eucalyptus urophylla. Die reaksie op besproeiingstoediening het getoon dat die kambium van bome in 'n eko-dormansiestadium was voor besproeiingstoediening. Met betrekking tot die besproeiingsbome gedurende die lenteperiode, het die resultate getoon dat die kambium aktief was gedurende laat-winter tot vroeë lente en daar was geen duidelike lente-aanvang effek nie. Reënval gedurende hierdie seisoen het nie merkbare effekte op houtvorming oor alle variëteite gehad nie. Die reaksie van die variëteite m.b.t. houtvorming was wel gekoppel aan verskillende maksimum temperature gedurende die lenteperiode. Eucalyptus urophylla was gevind om sensitief te wees vir daaglikse temperature bo 16°C, terwyl die ander variëteite sensitief was vir temperature bo 17°C. Gebaseer op die studie se resultate, is die gevolgtrekking dat in ʼn Mediterreense klimaat sekondêre houtvorming in Eucalyptus-variëteite beheer word deur hoe gunstig die omgewing is.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentv, 63 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130352en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshEucalyptus -- Ecologyen_ZA
dc.subject.lcshXylogenesisen_ZA
dc.subject.lcshWoody plantsen_ZA
dc.subject.lcshUCTDen_ZA
dc.titleCambial responsiveness in four eucalypt varieties to onset of drought as well as spring conditionsen_ZA
dc.typeThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
nevhungwili_cambial_2024.pdf
Size:
7.45 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Masters Degrees (Forest and Wood Science)