Growth and nutrition of Bruniaceae

Poole, Caroline Jacqueline (1999-12)

Thesis (M.Sc. Agric) -- University of Stellenbosch, 1999.

Thesis

ENGLISH SUMMARY: Bruniaceae are increasingly being harvested commercially as cut flowers in South Africa for the European cut flower markets. The need to cultivate certain species requires research to develop economically viable cultivation methods and the selection of productive cultivars. This study deals with horticultural and nutritional aspects of Bruniaceae, particularly Brunia albiflora (Pillans). Flower initiation and development of two species of Bruniaceae, Brunia albit/ora and Berzelia galpinii (Pillans) were investigated to determine when floral initiation occurred and to qualify progression of flower differentiation and development. It was observeq that development was six months apart with Brunia albiflora initiating florets in October and Berzelia galpinii in May. Carbohydrate studies were also carried out over a one year period, to determine seasonal changes of carbohydrates which would enable manipulation of cultural practices for increased yield. It was observed that new shoots had lower carbohydrate contents compared to flowering shoots. Side shoots of flowering shoots had higher starch and sugar content than main shoots after winter. The starch content decreased in side shoots following flower initiation in October, with the total sugar content of side shoots showing the same pattern. It appeared that side shoots were net carbohydrate sources and exported assimilates to the developing inflorescence. The increase in carbohydrates of the inflorescence was higher than the loss in the side shoots and it seems that Brunia albiflora is mainly reliant on current photosynthates for their growth. Soil and plant nutrient requirements of Brunia albiflora were investigated by selecting three localities in the Western Cape. Variation in terms of growth performance was large at each locality, presumably because of different soil types. Calcium in topsoils showed a significant negative correlation with plant performance, whereas higher exchangeable Na correlated with good plant performance. Soils with high clay-content seem to be unsuitable for Brunia albiflora possibly due to poor aeration. Positive correlations with plant performance were also found for organic carbon, N, P and K, as well as exchangeable acidity and exchange capacity of the B horizon. Leaf and stems were sampled at two dates to determine which component and time of sampling best reflected the nutrient status of the plant. Leaves were decided on as index tissues and sampling at anthesis (February) was appropriate. Leaf nutrient concentrations of Brunia albiflora were found to be low in N, P, K, Mg and Zn compared to other woody plant, whereas Ca, Cu and Mn appeared to have similar concentrations. The removal of macro-elements by cropping a plantation in full production was calculated as 38 kg N, 1.5 kg P, 35 kg K, 40 kg Ca and 5 kg Mg per hectare based on 25 flowering stems per plant and 5 000 plants per hectare. These results can be used as a basis for fertiliser recommendations, pending the results of fertiliser trials. As the demand for these flowers increases, there will be a greater demand for better quality. Improved production and flower quality should compensate for the extra costs of fertilisers.

AFRIKAANSE OPSOMMING: Bruniaceae word toenemend kommersieel as snyblom in Suid-Afrika geoes vir die Europese snyblommark. Die behoefte om sekere spesies kommersieel te kweek vereis navorsing om ekonomies vatbare verbouingsmetodes daar te stel en produktiewe kultivars uit te kies. Die studie handel oor hortologiese en voedingsaspekte van Bruniaceae, veral Brunia albiflora (Pillans). Blominisiasie en -ontwikkeling van twee spesie Bruniaceae, Brunia albiflora en Berzelia galpinii (Pillans) is gebruik om die tydstip van blominisiasie te bepaal en die verloop van blomdifferensiasie en -ontwikkeling te kwalifiseer. Die ontwikkeling van die twee spesies is ses maande uitmekaar, Brunia albiflora se blominisiasie is in Oktober, terwyl dit by Berzelia galpinii in Mei plaasvind. Koolhidraatveranderinge is oor een jaar bestudeer om die seisoenale veranderinge te bepaal om manipulasie van verbouingsmetodes vir verhoogde opbrengs daar te stel. Nuwe lote het 'n laer koolhidraatinhoud in vergelyking met blomdraende lote. Sylote van blomdraende lote het 'n hoer stysel- en suikerinhoud as hooflote. Die styselinhoud van sylote het verminder na die Oktober blominisiasie. Die totale suikerinhoud van sylote het dieselfde patroon gevolg. Daar is gevind dat sylote 'n bron van koolhidrate was, en ook assimilate na die ontwikkelende bloeiwyse uitgevoer het. Die styging in koolhidrate van die bloeiwyse was meer as die verlies in die sylote en dit blyk dat Brunia albiflora hoofsaaklik op huidige fotosintate staatmaak. Grond- en plantvoedingstofvereistes van Brunia albiflora is in drie lokaliteite in die Wes-Kaap ondersoek. Daar was groot variasie in plantprestasie by elke gebied, vermoedelik as gevolg van verskille in grondtipes. Kalsium in grond het 'n opvallende negatiewe korrelasie met plantprestasie getoon, terwyl hoer uitruilbare Na goeie plantprestasie getoon het. Grond met 'n hoe klei-inhoud blyk ongeskik vir Brunia albiflora te wees, moontlik as 'gevolg van swak deurlugting. Positiewe korrelasies is ook vir organiese koolstof, N, P en K, sowel as uitruilbare suurheid en die uitruil kapasiteit van die B horison gevind. Blare en stingels is op twee datums gemonster om vas te stel watter komponent en tyd van monsterneming die voedingstatus van die plant die beste weerspieel het. Daar is besluit om blare as indeksweefsel te gebruik en dat monsterneming by antese (Februarie) geskik is. Konsentrasies van N, P, K, Mg en Zn in die blare van Brunia albiflora was laag in vergelyking met ander houtagtige plante, terwyl, Ca, Cu en Mn soortgelyke konsentrasies getoon het. Die verwydering van makro-elemente ten tye van volle produksie is vasgestel as 38 kg N, 1.5 kg P, 35 kg K, 40 kg Ca en 5 kg Mg per hektaar, gebaseer op 25 blomdraende lote per plant en 5 000 plante per hektaar. Hierdie resultate kan gebruik word vir bemestingsaanbevelings in afwagting van die resultate van bemestingsproewe. Soos die aanvraag vir hierdie produk groter word, sal beter kwaliteit blomme verlang word. Verbeterde kwaliteit en produksie behoort te vergoed vir die bykomstige kostes van bemestingstowwe.

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