Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Reproductive bud development is the first step of sexual
reproduction of plants and is a major factor determining yield. For consistent yields
in pears, knowledge of the development of the reproductive bud is required.
The development of the reproductive bud with emphasis on the
primordial bourse shoot was studied. The bourse shoot is important because of the
ability of a bourse shoot to become reproductive, which can lead to bourse-overbourse
bearing. The progression of reproductive bud development in 'Forelle' and
'Rosemarie' was studied from primordial bourse shoot initiation until dormancy the
following season. The primordial bourse shoot was initiated in January 2003. The
primordial bourse shoot progressed during dormancy with a plastochron length of 60
days in June. The rate of preformed leaf formation increased rapidly until August
when the plastochron was 5 days. 'Rosemarie's' primordial bourse shoot
development was more advanced at full bloom, which is a possible reason for the
higher bourse-aver-bourse bearing habit of the cultivar. The number of leaves of the
bourse shoot was more than with the 'Forelle', which has a low tendency for bourseover-
bourse bearing. Flower initiation of the terminal bourse shoot bud was 56 and
77 d.a.f.b. for the 'Forelle' and 'Rosemarie', respectively. Initiation was well
correlated with bourse shoot growth cessation. An increase in mitotic activity
occurred during flower differentiation of the terminal bourse bud with a peak of floral
appendage formation during December and January. From February until dormancy
enlargement of the floral parts took place.
The influence of severe dormant pruning and the quality of 2-
year-old wood, on reproductive bud sink strength of 'Packham's Triumph' trees were
investigated. The sink strength of primary growth increased by 40 % for short
bearing units (SBU's) and 140 % for thick bearing units (BU's) as compared to long
bearing units (LBU's) and thin BU's respectively. The increase in primary growth
was due to better fruit set and larger fruit in the SBU's and the thick BU's. Since the
increase in primary growth is less for SBU's compared to thick BU's the conclusion,
which can be made, is that branch diameter influenced sink strength more than branch
length. With increase in branch diameter the size of the xylem transport system
increases more than that of the phloem. The increase in xylem transported metabolites, in particular root derived cytokinin seems to predominantly influence the
magnitude of the sink strength.
The influence of scoring and 6-benzyladenine (BA) application,
during the flower induction phase on 'Doyenne du Cornice' and 'Rosemarie', were
studied. Scoring caused a 50 % increase in fruit number of 'Doyenne du Cornice',
which resulted in a 38 % increase in yield compared to the control. The increase in
fruit number was due to higher percentage reproductive buds and improved bud
quality. For the 'Rosemarie' scoring at the correct time resulted in a 40 % increase in
reproductive buds. Scoring disrupts basipetal transport in the phloem, which results
in the removal of apical dominance and an increase in root derived cytokinin's. More
meristems can respond to inductive conditions and high quality reproductive buds
develop. The combination of BA and scoring, lead to more flowers per inflorescence
in 'Doyenne du Cornice'. / AFRIKAANSE OPSOMMING: Reproduktiewe knopontwikkeling by die peer
Reproduktiewe knopontwikkeling is die eerste fase van
reproduktiewe voortplanting in plante en is belangrik, want dit bepaal die oesgrootte.
Vir konstante oeste in peerproduksie moet reproduktiewe knopontwikkeling verstaan
word.
Die ontwikkeling van die reproduktiewe knop, meer spesifiek
die primordiale beursloot is bestudeer. Die beursloot is belangrik a.g.v. die beurs-oorbeurs
drawyse. Die ontwikkeling van die reproduktiewe knop van 'Forelle' en
'Rosemarie' is gevolg. Die primordiale beursloot is Januarie 2003 geinisieër en
ontwikkel tydens die boom se dormante fase met 'n plastochron van 60 dae gedurende
Junie. Preformeerde blaarvormingstempo neem toe tot Augustus waar die
plastochron 5 dae is. 'Rosemarie' se primordiale beursloot ontwikkeling was meer
gevorderd teen volblom, met meer beurslootblare reeds teenwoordig. Dit is dalk die
rede vir die hoër tendens van beurs-oor-beurs drag van die kultivar in vergelyking met
'Forelle'. Die terminale beurslootknop is 56 en 77 dae na volblom geïniseer vir
'Forelle' en 'Rosemarie' respektiewelik. Inisiasie was goed gekorreleerd met
beeïndiging van beurslootgroei. Blomdifferensiasie het inisiasie gevolg met 'n
toename in mitotiese aktiwiteit, blomaanhangsel vorming het 'n piek bereik III
Desember en Januarie. Vanaf Februarie tot dormansie het ontwikkeling hoofsaaklik
in vergroting van blomorgane plaasgevind.
Die invloed van strawwe dormante snoei en die kwaliteit van
2-jaar-oue dra-eenhede op sinksterkte van reproduktiewe knoppe van 'Packham's
Triumph' pere is ondersoek tydens die 2002/03 seisoen. Die sinksterkte van primêre
groei het 40 % toegeneem vir kort dra-eenhede en 140 % vir dik dra-eenhede in
vergelyking met lang dra-eenhede en dun dra-eenhede respektiewelik. Die toename
in primêre groei vir kort en dik dra-eenhede kon toegeskryf word aan beter vrugset en
groter vrugte. Omdat die toename in sinksterkte minder is vir kort dra-eenhede in
vergelyking met dik dra-eenhede kan die afleiding gemaak word dat dra-eenheiddikte
sinksterkte meer beïnvloed as dra-eenheidlengte. Met 'n toename in dra-eenheiddikte, neem xileemvaatweefsel meer toe as floeëmvaatweefsel. 'n Toename in xileem
getranslokeerde metaboliete, meer spesifiek wortel vervaardigde sitokiniene
beïnvloed die sinksterkte van die reproduktiewe knoppe.
Die invloed van ringelering (ringsnit deur floeëm sonder bas
verwydering) en 6-bensielaldenien (BA) toediening tydens reproduktiewe
knopinduksie van 'Doyenne du Cornice' en 'Rosemarie' is ondersoek. Ringelering
het 'n 50 % toename in vrugaantal veroorsaak wat die oes met 38 % laat toeneem het
in vergelyking met die kontrole, vir 'Doyenne du Cornice'. Die toename in vrugte was
a.g.v. 'n hoër persentasie reproduktiewe knoppe en toename in blomkwaliteit. By
'Rosemarie' het ringelering 'n 40 % toename in reproduktiewe knoppe bewerkstellig.
Ringelering onderbreek die basipetale vervoer in die floeëm, verwyder dus apikale
dominansie, met die gevolg dat daar 'n toename in wortel geproduseerde sitokiniene
is. Meer meristeme reageer op induktiewe toestande en reproduktiewe knoppe van
hoë kwaliteit vorm. Die kombinasie van ringelering en BA -toediening het meer
blomme per reproduktiewe knop veroorsaak.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50079 |
| Date | 03 1900 |
| Creators | Reynolds, Louis Percy |
| Contributors | Theron, K. I., Jacobs, G., Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 74 p. : ill. |
| Rights | Stellenbosch University |
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