Thesis (MScAgric)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Protea cut flowers are exported worldwide but the vase life of some species and cultivars
is considerably shortened by post-harvest leaf blackening. Research has established
carbohydrate depletion to be positively correlated with this disorder. Consequently, a
study had been made of the carbohydrate status of various species and cultivars, as well
as the effect of supplemental glucose (pre and post-storage) on leaf blackening.
Glucose, fructose, sucrose and starch concentrations of various Protea species and
cultivars held in water were measured at harvest, and again at leaf blackening initiation.
All measured carbohydrates declined significantly in 'Carnival', 'Pink Ice' and 'Sheila'.
In 'Cardinal' all carbohydrate concentrations decreased significantly, except the sucrose
concentration in the inflorescence. 'Susara' and 'Ivy' had very high initial carbohydrate
concentrations in the leaves which decreased significantly. The very high initial
carbohydrate concentrations in the inflorescence of 'Ivy' declined significantly. 'Brenda'
differed from the other cultivars and species in that glucose concentrations increased over
time. Carbohydrate concentrations of most of the tested proteas declined significantly
from harvest to the initiation of leaf blackening. This highlighted the dependence of the
leaves and inflorescence on the carbohydrate reserves, further substantiating the
carbohydrate depletion theory. The inflorescences were characterized by high fructose
and glucose concentrations and low sucrose concentrations when compared to the leaves. It was hypothesized that glucose pulsing and cold storage at 1°C for three weeks would
significantly reduce leaf blackening. 'Brenda', 'Cardinal', 'Carnival', 'Pink Ice',
'Susara ' and 'Sylvia' had significantly less leaf blackening with glucose treatments of 4
and 10%. Leaf blackening of 'Sheila', P. cynaroides and P. grandiceps was not
significantly reduced by glucose pulsing. P. magnifica showed a small, but significant,
reduction in leaf blackening in response to the 3, 6 and 9% treatments after 10 days only,
but despite this, leaf blackening was unacceptably high. 'Pink Ice' harvested at the soft
tip stage had less leaf blackening than those harvested open or closed. Toxicity
symptoms on the leaves, and in some instances flowers, were observed at higher glucose
concentrations (8 and 10%) onP. grandiceps, P. cynaroides, 'Cardinal' and 'Sheila'. All
glucose treatments resulted in toxicity symptoms on P. magnifica. A decrease in nonstructural
carbohydrates post-harvest apparently occurs in all proteas but it appears that
only members of the Ligulatae respond to glucose.
Glucose pulsing followed by cold storage at 1°C for three weeks in combination with
post-storage glucose vase solutions, significantly reduced leaf blackening of some Protea
cultivars. Glucose (1 and 2%), with hypochlorite, significantly delayed leaf blackening
in 'Cardinal' and 'Sylvia' after seven days. Leaf blackening of 'Brenda', 'Carnival',
'Pink Ice' and 'Susara' was not significantly reduced by the glucose vase solutions.
Other disinfectants, in combination with the sugar treatments, need to be evaluated since
the hypochlorite treatment had a dehydrating effect on all the cultivars and resulted in
increased leaf blackening. Carbohydrate supplementation of protea flowers with glucose, pre and post-storage, will
help meet the post-harvest carbohydrate requirements of certain Protea cultivars and
species to an extent. Glucose treatments must be seen in conjunction with maintaining
the cold chain and when combined with cold chain maintenance, can extend the storage
and vase life. / AFRIKAANSE OPSOMMING: Protea snyblomme word wêreldwyd uitgevoer alhoewel die vaasleeftyd van sommige
spesies en kultivars beduidend verkort word deur na-oes loof verbruining. Navorsing het
koolhidraatverbruik positief gekorreleer met hierdie probleem. Gevolglik is 'n studie
gemaak van die koolhidraatstatus van verskeie spesies en kultivars asook die effek van
addisionele glukose (voor en na opberging) op loofverbruining.
Glukose, fruktose, sukrose en stysel konsentrasies van verskeie Protea spesies en
kultivars wat in water gehou is, is bepaal met oes en weer met die eerste tekens van
loofverbruining. Al die gemete koolhidraatkonsentrasies het beduidend afgeneem in
'Carnival', 'Pink Ice' en 'Sheila'. In 'Cardinal' het al die koolhidraatkonsentrasies
beduidend afgeneem, behalwe vir die sukrosekonsentrasie in die blom. 'Susara' en 'Ivy'
het baie hoë begin koolhidraatkonsentrasies in die blare wat beduidend afneem. Die baie
hoë inisiële koolhidraatkonsentrasies in die blom van 'Ivy' neem beduidend af met tyd.
'Brenda' verskil van die ander kultivars en spesies deurdat die glukosekonsentrasies
toeneem met tyd. Koolhidraatkonsentrasies van die meeste getoetste proteas neem
beduidend af vanaf oes totdat die eerste tekens van loofverbruining verskyn. Dit het die
afhanklikheid van die blare en blom op die koolhidraatreserwes beklemtoon en daardeur
verder die koolhidraatteorie ondersteun. Die blomme is gekarakteriseer deur hoë
fruktose- en glukosekonsentrasies en lae sukrosekonsentrasies wanneer dit met die blare
vergelyk is.Die hipotese is gestel dat die voorsiening van glukose, vir 'n aantal ure, gekombineerd
met koue opberging by 1°C vir drie weke loofverbruining beduidend sal verminder.
'Brenda', 'Cardinal', 'Carnival', 'Pink lee', 'Susara' en 'Sylvia' het beduidend minder
loofverbruining met glukose behandelings tussen 4 en 10%. Loofverbruining van
'Sheila', P. cynaroides en P. grandiceps is nie beduidend verminder deur glukose
behandelings nie. P. magnifica het 'n klein, maar beduidende verlaging in
loofverbruining getoon met die 3, 6 en 9% behandelings na 10 dae, maar ten spyte
hiervan was loofverbruining onaanvaarbaar hoog. 'Pink lee' is geoes by die sagte punt
stadium en het minder loofverbruining gehad as blomme wat oop of toe geoes is.
Toksisiteitsimptome op die blare, en in sommige gevalle blomme, is waargeneem met
hoër glukose konsentrasies (8 en 10%) op P. grandiceps, P. cynaroides, 'Cardinal' en
'Sheila'. Alle glukosebehandelings het toksisiteitsimptome tot gevolg gehad op P.
magnifica. 'n Afname in nie-strukturele koolhidrate na oes kom waarskynlik voor in alle
proteas maar dit wil voorkom of slegs lede van die Ligulatae positief reageer op glukose.
Glukosebehandeling gevolg deur koue opberging by 1°C vir drie weke in kombinasie met
na-stoor glukose vaasoplossings het loofverbruining van sommige Protea kultivars
beduidend verminder. Glukose (l en 2%), saam met hipoehloriet, het loofverbruining
beduidend verminder in 'Cardinal' en 'Sylvia' na sewe dae. Loofverbruining van
'Brenda', 'Carnival', 'Pink lee' en 'Susara' is nie beduidend verminder deur die glukose
vaasoplossings nie. Ander ontsmettingsmiddels in kombinasie met die
suikerbehandelings moet geëvalueer word aangesien die hipoehlorietbehandeling 'n dehidrerende effek op al die kultivars gehad het en 'n toename in loofverbruining tot
gevolg gehad het.
Byvoeging van glukose by proteablomme, voor en na opberging, sal tot 'n mate help om
in die na-oes koolhidraatbehoeftes van sekere Protea kultivars en spesies te voorsien.
Glukosebehandelings moet saam met die beheer van die koueketting gesien word en
wanneer gekombineerd met koueketting beheer kan dit opberg en vaasleeftyd verleng.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53320 |
| Date | 12 1900 |
| Creators | Meyer, Celeste |
| Contributors | Jacobs, G., Holcroft, D. M., Stellenbosch University. Faculty of AgriSciences. Dept. of Horticultural Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 93 p. |
| Rights | Stellenbosch University |
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