Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Various researchers have determined that salinity causes several kinds of damage to
plants such as germination inhibition, metabolic disturbances, yield reduction and quality
losses. However, the severity of salt damage has been found to be dependent on the
cultivar, level of salinity, period of exposure to salinity, and the growth stage of the plant.
An understanding of the severity of salinity and its potential negative impacts on crops is
essential to optimise production. Knowledge of seed vigour, expressed as germination
percentage and germination rate at the optimum temperature for germination, would
provide growers with valuable information to measure and compare the viability of seed
lots.
A study was done where fresh and aged seeds of two watermelon cultivars were
investigated in germination tests under laboratory conditions at four salinity levels and
five temperature regimes. The best germination was achieved at 4 mS cm-1 for both
cultivars, Odem and Paladin. At 8 mS cm-I, the germination percentage for Paladin was
31% better than for Odem. The germination time for aged Odem seeds was significantly
delayed at this EC 8 level but ageing of Paladin seeds had no detrimental effect at this EC
level. Paladin germinated significantly better than Odem at the relatively low temperature
range of I5-20°C, indicating that it is well-adapted for early planting.
A new plant growing system, using vertical training of two shoots was tested in a
greenhouse, aiming to optimise the growth regulating capabilities of this crop
environment. Traditional watermelons are open-field planted in rows at low densities.
Even with this plant spacing, by harvesting time the vines are spread in such a way that
the foliage laterally covers the inter-row spacing, making cultivation practices such as
spraying, weeding and harvesting difficult and almost impossible. The production of
greenhouse crops is advantageous, but involves a number of cultural inputs and
techniques for optimum yields. The effects of plant pruning systems and salinity levels on
watermelon cultivars (Odem and Paladin) in a low-cost greenhouse were studied using a
drain-to-waste fertigation system. Changing the nutrient solution from a low salinity level (EC 4 mS cm1) during vegetative growth to EC 4 mS cm-I after pollination, did not
reduce fruit mass, but significantly increased the sugar yield of Odem, the icebox-type
cultivar. Excessive pruning (less leaves per shoot) was more efficient with low salinity
levels than at a high salinity level. Moderate pruning (more leaves per shoot) represented
a good system, producing fruits of lesser weight and acceptable quality. / AFRIKAANSE OPSOMMING: Verskeie navorsers het reeds die skadelike gevolge van brak toestande op ontkieming,
plant metabolisme, opbrengs en kwaliteit van gewas plante ondersoek. Die omvang van
die skade kan deur kultivars, die konsentrasie soute, die periode van blootstelling asook
plante se groeistadium bepaal word. 'n Goeie begrip van die potensiële skadelikheid van
hoë sout konsentrasies op gewasse is nodig om produksie te optimaliseer. Inligting oor
die kiemkragtigheid van saad, uitgedruk as die persentasie ontkieming asook die
ontkiemingstempo, is vir kwekers nodig ten einde te verseker dat goeie saad gebruik kan
word.
'n Ondersoek is gedoen waar vars asook verouderde saad van twee waatlemoen kultivars
onder laboratorium toestande by vier sout peile en vyf temperature ontkiem is. Die beste
ontkieming vir beide kultivars, Odem en Paladin, is gevind waar die elektriese geleiding
(Eï,') 4 mS cm-1 was. Teen 8 mS cm-1 was die persentasie ontkieming vir Paladin 31%
beter as vir Odem. Veroudering van Odem saad het 'n betekenisvol swakker
ontkiemingstempo met'n Ee van 8 mS cm-1 getoon terwyl verouderde Paladin saad nie
by hierdie Ee swakker vertoon het nie. Paladin het by die relatief lae temperatuur sone
van 15-20oe betekenisvol beter as Odem saad ontkiem wat daarop dui dat dit vir vroeë
aanplantings geskik is.
'n Nuwe produksiestelsel, waar twee lote per plant vertikaal in 'n V-vorm opgelei is, is in
'n kweekhuis getoets in 'n poging om die groeiregulerende potensiaal van so 'n
omgewing te optimaliseer. Waatlemoene word tradisioneel in rye teen 'n lae plantdigtheid
in veldaanplantings verbou. Met so 'n praktyk ontwikkel daar soveel ranke
tussen die rye dat praktyke soos onkruid beheer, plaagbeheer en oes bemoeilik word. Die
produksie van gewasse in kweekhuise hou voordele in maar 'n aantal insette en spesiale
tegnieke is nodig vir optimum opbrengs. Die invloed van snoeipraktyke en soutpeile is
met twee waatlemoen kultivars (Odem en Paladin) in 'n lae-koste kweekhuis ondersoek
deur 'n sisteem te gebruik waar voedingsoplossings in vry dreinerende sakke met
saagsels gedrup is. Waar die Ee van die voedingsoplossing voor vrugset 2 mS cm-1 was en toe vir die periode van vrugontwikkeling tot 4 mS cm-1 verhoog is, het geen vrugverkleining
by Odem gevolg nie terwyl die suikeropbrengs wel verhoog het. Oormatige
verwydering van blare was minder skadelik met 'n lae EC as waar die EC hoog was. 'n
Matige snoeiproses met meer blare per loot, het 'n goeie produksie van aanvaarbare vruggrootte
en 'n goeie kwaliteit verseker.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50361 |
| Date | 03 1900 |
| Creators | Kuvare, Uparura S. K. (Uparuru Silvanus Karl) |
| Contributors | Combrink, N. J. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 64 pages : illustrations |
| Rights | Stellenbosch University |
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