Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Low crop productivity in arid and semi-arid regions is a
problem caused by water stress as well as associated high levels
of soil and water salinity. An increased demand for salt
tolerant crops is experienced in these regions. Amaranth is a
glycophyte and C4 dicotyledonous crop, well adapted to arid and
semi-arid regions. Previous studies on the physiological
response of salt-stressed amaranths have indicated that this
crop is salt tolerant. As vegetable, amaranths can be harvested
by uprooting and by topping. The most common harvesting method
is by topping, allowing repeated harvesting. When harvested by
topping, the cutting height is an important parameter that may
be manipulated to optimise growth rates. In this study, plants
were exposed to different salt stress levels and harvesting
procedures while yield and quality of Amaranthus tricolor were
investigated. Nutrient solutions at four different electrical
conducti vi ty (EC) levels were used to fertigate the plants. At
high EC levels (4 mS cm-l and 8 mS cm-lj, the length and diameter
of main stems, internode lengths, stem weights as well as root
weights were reduced, especially with a longer growth period.
However, the shoot: root ratio and leaf protein yields increased
and flowering was delayed. The best leaf yield was obtained
where plants were fertigated at an EC of 4 mS cm-l for 45 days.
The cutting height did not affect leaf yield, growth rates and
leaf protein yield in plants fertigated at EC levels of 1, 2 and
4 mS cm-l. At an EC of 8 mS cm-l, the growth rate recovered to a
value similar to that of plants fertigated with an EC of 2 mS cmonly
where plants were topped at 25%. With this less
destructive cutting height (topped at 25%), leaf yields, growth
rates and ·leaf calcium and protein yields at an EC of 8 mS cm"
were superior to that of plants topped at 50%. In plants topped
at 25%, the recovered growth rates at EC 8 mS cm-l was probably
due to more photosynthetic active tissue left after cuttings, resulting in the accumulation of compatible solutes for osmotic
adjustment. / AFRIKAANSE OPSOMMING: Die invloed van soutstremmings en oesprosedures op die groei,
ontwikkeling en blaarkwaliteit van Amaranthus trico~or L.
Lae produksie van gewasse in ariede en semi-ariede gebiede is
'n probleem wat veroorsaak word deur watertekorte asook geassosieerde
hoë peile van grondverbrakking en soute in water. 'n
Verhoogde vraag na soutverdraagsame gewasse word in hierdie
gebiede ervaar. Amaranthus is 'n glikofiet en dikotiele C4 gewas
wat goed in ariede en semi-ariede streke aangepas is. Vorige
ondersoeke oor die fisiologiese reaksie van Amaranthus op
soutstremmings het daarop gedui dat die gewas soutverdraagsaam
is. As groentegewas word dit ge-oes deur dit uit te trek of deur
dit gereeld te top. Waar dit getop word is die oes-tophoogte 'n
belangrike parameter wat gemanipuleer kan word om die groeitempo
te optimaliseer. In hierdie ondersoek is plante aan verskillende
peile van soutstremmings en oesprosedures blootgestel terwyl die
opbrengs en kwaliteit van Amaranthus tricolor ondersoek is.
Voedingsoplossings is teen vier elektriese geleidingspeile (EC)
gebruik om plante te voedsproei. Teen hoë EC peile (4 mS cm-l en
8 mS cm-l
), het lengtes en die deursnit van hoofstamme, internode
lengtes, stam massas en wortelmassas afgeneem, veral met lang
groeiperiodes. Die
opbrengs het egter
bogroei:wortel verhouding en
toegeneem terwyl blomvorming
blaarproteien
vertraag is.
Die beste blaar opbrengs is na 45 dae verkry waar plante teen 'n
EC van 4 mS cm-l gevoedsproei is. Oes-tophoogte het nie blaar
opbrengs, groeitempo of blaar protei en opbrengs beïnvloed met EC
waardes in voedingsoplossings van 1, 2 en 4 mS cm-l nie. Met' n
EC van 8 mS cm-l het die groeitempo herstel tot 'n vlak,
gelykwaardig aan wat by 'n EC van 2 mS cm-l verkry is, slegs waar
teen 25% tophoogtes ge-oes is. Met hierdie minder destruktiewe
oesmetode (oes-tophoogte 25%), was blaar opbrengs, groei tempo
en blaar kalsium en -proteien opbrengste by 'n EC van 8 mS cm-l
betekenisvol beter as waar die oes-topdiepte 50% was. Plante wat met 25% topdieptes ge-oes is se herstel in groetempo teen EC 8
mS cm-1 was waarskynlik te danke aan meer fotosinteties aktiewe
materiaal wat na oes op plante gelaat is. Dit kon tot die
akkumulasie van oplosbare stowwe en osmotiese aanpassings aanleiding gegee het.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53746 |
| Date | 03 1900 |
| Creators | Ribeiro, J. E. M. M. (Jeronimo Ernesto Meneses Machado) |
| 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 | 76 p. : ill. |
| Rights | Stellenbosch University |
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