Thesis (MScAgric)--University of Stellenbosch, 1994 / 127 Leaves printed single pages, preliminary pages i-viii and numberd pages 1-118.Includes bibliography,tables and figures. / Date on t.p.: Dec. 1994. / ENGLISH ABSTRACT: Effects of pH,sucrose, boric acid and temperature on in vitro germination of pollen of
Protea repens (L.) L. cv. 'Embers' were investigated in hanging-drop culture to establish
optimum conditions for germination. Optimum values were found within ranges pH: 5 - 8,
sucroseconcentration:0.4 - 0.7 M, boric acid concentration:50 - 500 mg.e-1
, and incubation
temperature: 5 - 30°C. Storage temperature and humidity on pollen viability was studied
in four Pro tea clones. Pollen was stored at a range of temperatures and relative humidities
for up to one year and tested for ability to germinate in vitro. Pollen of P. repens cv.
'Sneyd', P. eximia cv. 'Fiery Duchess' andP. magnifica clone 'T 84 07 OS', stored in liquid
nitrogen (-196°C) and in a freezer (-14° to -18°C), retained a germination percentage as high
as that of fresh pollen regardless of humidity. The study showed that long-term storage of
protea pollen is not feasible at temperatures above O°C. The correlations between the
fluorochromatic reaction (FCR) and germinability were found to be low and nonsignificant.
Fifteen month old cryopreserved 'Sneyd' pollen was shown to retain its ability to fertilize and
set seed equal to that of fresh pollen. 'Sneyd', 'Fiery Duchess' and 'T 84 07 OS' pollen
could be repeatedly thawed and frozen in liquid nitrogen before its germinability in vitro
decreased. The morphology and size of Protea pollen was studied, using light and scanning
electron microscopy. Polymorphic grains were observed in two interspecific hybrids. Very
small differences in pollen grain size were recorded between clones/species. The male
fertility of 25 interspecific Pro tea hybrids, based on in vitro pollen germinability, was
investigated. The majority of hybrids were found to be sufficiently fertile to be used in a
breeding programme. Pistil structure and pollen tube pathways were investigated in 'Sneyd'
using light and scanning electron microscopy. The pistil had four distinct regions, consisting
of the stigma, the vertebra-shaped upper style, the heart-shaped lower style, and the ovary.
The pistil had a stylar canal along its entire length and this canal was also the route by which
pollen tubes grew to the ovary. Very low numbers of pollen tubes reached the ovary. The
breeding system of 'Sneyd' and 'Fiery Duchess' were determined from pollen tube and seed
set data, after controlled hand-pollinations. Both clones were found to be fully selfcompatible.
Very low percentages autogamous seed set were recorded. Interspecific crosses
had a low success rate. An incompatibility reaction probably occurred on the stigma and/or in the upper style regions.The attainment of maximum stigma receptivity of two Protea
cultivars was investigated by means of seed set experiments, pollen tube growth observations
and measurement of the degree of opening and closing of the stigmatic groove. Both
cultivars were found to be protandrous. The maximum stigmatic groove width of both
cultivars never exceeded the pollen grain diameter. It was concluded that Protea spp. must
be hand-pollinated two to six days after anthesis in order to obtain maximum seed set; while
for the observations of pollen tubes in the ovary, inflorescences must not be harvested before
seven days after pollination. / AFRIKAANSE OPSOMMING: Ten einde 'n optimale medium vir die in vitro-ontkieming van Protea-stuifmeel te
ontwikkel, is die effek van pH, sukrose, boorsuur, en temperatuur op die in vitro-ontkieming
van Protea repens (L.) L. cv. 'Embers'-stuifmeel deur middel van die hangdruppel-metode
ondersoek. Die volgende reekse van veranderlikes wat getoets is, is as optimaal gevind;
pH: 5 - 8, sukrosekonsentrasie: 0.4 - 0.7 M, boorsuurkonsentrasie: 50 - 500 mg.e-1 en
inkubasietemperatuur: 5 - 30°C. Die invloed van bergingstemperatuur en humiditeit op
stuifmeel-Iewenskragtigheid is in vier Protea-klone ondersoek. Stuifmeel is gestoor by 'n
reeks temperature en relatiewe humiditeite vir tot eenjaar, en vir in vitro-ontkiemingsvermoe
getoets.' Stuifmeel van P. repens <?v. 'Sneyd', P. eximia cv. 'Fiery Duchess', en P.
magnifica kloon'T 84 07 OS', in vloeibare stikstof (-196°C) en in 'n vrieskas (-14° tot -
18°C) geberg, het 'n ontkiemingspersentasie gelykstaande aan die van vars stuifmeel
gehandhaaf, ongeag van die humiditeit. Hierdie studie het verder aangetoon dat
langtermynberging van Protea-stuifmeel bokant O°C me die moeite werd is me. Die
korrelasie tussen die fluorochromatiese reaksie (FCR) en ontkieming was laag en me
betekemsvol me. 'Sneyd' -stuifmeel wat vir 15 maande in vloeibare stikstof gestoor is, het
die bevrugtings- en saadsetvermoe gelykstaande aan vars stuifmeel behou. 'Sneyd', 'Fiery
Duchess' en 'T 84 07 OS'-stuifmeel kon herhaaldelik in vloeibare stikstof gevries en ontdooi
word voordat hul ontkiemingsvermoe afgeneem het. Die morfologie en grootte van Proteastuifmeel
is deur middel van lig- en skandeerelektronmikroskopie bestudeer. Polimorfiese
stuifmeelkorrels is in twee interspesie-hibriede waargeneem. Baie klein verskille in
stuifmeelkorrelgroottes het tussen klone/spesies voorgekom. Die manlike vrugbaarheid van
25 Protea-interspesiehibriede, gebaseer op die in vitro-ontkiembaarheid, is ondersoek. Dit
is gevind dat die meerderheid hibriede 'n voldoende graad van vrugbaarheid het om in 'n
teelprogram te gebruik. Die stamperstruktuur en stuifmeelbuiswee in P. repens is deur
middel van lig- en skandeer-elektronmikroskopie ondersoek. Die stamper bestaan uit vier
kenmerkende gebiede, naamlik die stempel, die werwelvormige bo-styl, die hartvormige
onderstyl, en die vrugbeginsel. Die stamper het 'n stylkanaal regdeur die totale lengte van
die stamper, en hierdie kanaal is ook die weg waarvolgens stuifmeelbuise na die vrugbeginsel gegroei het. Min stuifmeelbuise het die vrugbeginsel bereik. Die teelsisteem van 'Sneyd'
en 'Fiery Duchess' is deur middel van stuifmeelbuis- en saadsetdata na gekontroleerde
handbestuiwings ondersoek. Beide kIone was ten volle selfverenigbaar. Die persentasie
outogame saadset was baie laag. Interspesiekruisings het 'n baie lae sukses gehad. Dit is
voorgestel dat die onverenigbaarheidsreaksie in die stempel en/of in die bopunt van die styl
plaasvind. Die bereiking van maksimum stempelontvanklikheid van twee Protea-cultivars
is deur middel van saadseteksperimente, stuifmeelbuisdata en waarnemings van die oop- en
toemaak van die stempelgroef ondersoek. Beide cultivars was protandries. Die maksimum
stempelgroefwydte het nooit die stuifmeelkorreldeursnee oorskry nie. Dit is afgelei dat
Protea-spesies twee tot ses dae na antese handbestuif moet word vir optimale saadset. Vir
die waarneming van stuifmeelbuise in die vrugbeginsel, moet bloeiwyses nie voor sewe dae
na bestuiwing geoes word nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16084 |
| Date | 03 1900 |
| Creators | Van der Walt, Izak David |
| Contributors | De Bruyn, J. A., Retief, A. E., Littlejohn, G. M., University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics, Jacobs, Ivan |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 118 p. : ill. |
| Rights | University of Stellenbosch |
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