The influence of boron at different calcium levels on the growth, yield and mineral content of canola, Brassica napus L.

Hanekom, Dirk Johan (1999-12)

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

Thesis

ENGLISH ABSTRACT: Oilseed rape plants were grown in pots in two glasshouse trials during 1992 and 1993. Plants received 2 calcium (Ca) rates and 4 boron (B) rates in a factorial design. During the first experiment B rates were 0.2, 0.5, 0.8 and 1.1 and 0.1, 0.5, 0.8 and 1.1 ppm during the second experiment. Ca rates were 117.4 and 182.1 during the first experiment and 56.7 and 182.1 ppm during the second experiment. A study of the vegetative growth showed that, Ca had no consistent effect on growth or the parameters measured, nor did it show any interaction with B. In general B application rates during the first experiment had little effect on vegetative growth. During the second experiment low B (0.1 ppm) had a significant influence on most of the variants measured. Leaf-, stem-, and root growth as well as total plant dry matter were detrimentally affected at the later stages of plant development. Analysis of the reproductive growth showed that, Ca had no significant effect on the parameters measured, nor did it show any interaction with B. B application rates during the first experiment had no significant effect on the amount of pods, pod mass, seeds per pod, thousand kernel mass or dry mass of crop residue, but did affect the amount and mass of seeds produced per plant. During the second experiment low B (0.1 ppm) had a significant effect on the formation of pods and the production of seeds. The amount of pods, pod mass, seeds per pod, seeds per plant, seed mass per plant, dry mass of crop residue and harvest index (HI) were all negatively affected. High B (1.1 ppm) had a positive effect on the thousand kernel mass (TKW). Leaf, stem and pods from the second experiment (1993) were analyzed at different sampling dates to determine the influence of Ca and B application on the accumulation of elements in different plant organs. The data confirmed that levels of all elements vary between plant tissues and with their physiological age. Ca, Mg, Mn and B tend to build up in the leaf tissue of the plant while N, P, K, Na, Cu, Zn and Fe were diluted at rates that depended on the growth of the specific plant part analyzed. The effect of applied Ca on plant Ca content was small and Ca effects on the concentrations of most elements were very small or negligible and unclear. Some effects on K and Mg were observed and can be explained by differences in the concentrations applied due to cation corrections. Low B (0.1 ppm) resulted in elevated levels of N, P, K, Ca and Mg in the main- and side stem tissue which was probably caused by a reduction in growth of these plant parts induced by B deficiency. The only consistent effect of B was a negative effect on the Mn content of all of the tissue analyzed. B appeared to accumulate in the leaf. but not in the stem as the plants aged, making the latter more suitable for analysis when physiological age of tissue cannot be accounted for. Low B (0.1 ppm) caused low B values in stem tissue but increasing B levels did not increase the B concentrations in tissue to follow linearly. This could give a false indication of availability of B as higher B applications were not reflected in tissue levels. As B tend to accumulate in leaf tissue the physiological age of leaf tissue is therefore critical when used for analysis. B content in leaf tissue followed the application rates more closely than that of other tissue analyzed and gave a better indication of availability of B, but was dependent on the physiological age of the tissue.

AFRIKAANSE OPSOMMING: Olieryke raapsaad (canola) is gedurende 1992 en 1993 in twee glashuis potproewe verbou. Twee kalcium (Ca) vlakke en 4 boor (B) vlakke is as behandelings in 'n faktoriaal proefontwerp toegedien. B toedieningsvlakke gedurende die eerste eksperiment was 0.2,0.5,0.8, en 1.1 dpm en 0.1,0.2, 0.8, 1.1 dpm gedurende die tweede eksperiment. Ca-toedieningsvlakke was 117.4 en 182.1 dpm gedurende die eerste eksperiment en 56.7 en 182.1 dpm gedurende die tweede eksperiment. 'n Ondersoek na die vegetatiewe groei het getoon dat Ca geen konstante effek gehad het op die die parameters wat gemeet is nie asook geen interaksie met B nie. Oor die algemeen het Btoedieningsvlakke gedurende die eerste eksperiment weinig effek op die vegetatiewe groei gehad. Gedurende die tweede eksperiment het die lae B vlak (0.1 dpm) 'n betekenisvolle invloed op die meeste van die parameters wat gemeet is, gehad. Blaar-, stingel- en wortelgroei, sowel as totale plant droemateriaal is nadelig beinvloed by die gevorderde stadiums van plantontwikkeling. Analise van die reproduktiewe groei het getoon dat Ca geen betekenisvolle invloed op die parameters gemeet, gehad het nie en het ook geen interaksie met B gelewer nie. B toedieningsvlakke gedurende die eerste eksperiment het geen betekenisvolle verskille op die aantal peule gevorm, peul massa, sade per peul, duisendkorrelmassa of droemassa van oesreste nie gehad nie, maar het weI die aantal en massa saad geproduseer per plant, beinvloed. Gedurende die tweede eksperiment het lae B-toedieningsvlakke (0.1 dpm) 'n betekenisvolle effek op die vorming van peule asook saadset gehad. Die aantal peule en peulmassa per plant, sade per peul, sade per plant, saadmassa per plant, droe massa van oesreste en oesindeks (01) is almal negatief beinvloed. Hoe B-toediengsvlakke (1.1 dpm) het 'n positiewe effek op die 0l gehad. Plantmateriaal van die tweede eksperiment is in 'n afsonderlike studie geanaliseer ten einde die invloed van behandelings op die minerale inhoud te bepaal. Blaar, stam en peulweefsel is op verskillende tye gemonster en ontleed om die invloed van Ca en B toedieningsvlakke op die akkumulasie van verskillende elemente in die verskillende plantorgane te bepaal. Die data het bevestig dat vlakke van elemente tussen verskillende plantweefsel wissel asook met die fisiologiese ouderdom van die weefsel. Ca, Mg, Mn en B het geneig om in die blaarweefsel te akkumuleer terwyl N, P, K, Na, Cu, Zn en Fe 'n verdunningseffek ondergaan het, wat gewissel het na gelang van die groeipatroon van die spesifieke plantweefsel. Die invloed van toegediende Ca op die Caplantinhoud was gering of onduidelik. 'n Mate van reaksie op K en Mg is waargeneem, maar is toegeskryf aan toedieningsvlakke van die elemente weens katioon korreksie. Lae B vlakke (0.1 dpm) het verhoogde N, P, K, Ca, en Mg vlakke in die stamweefsel tot gevolg gehad en is waarskynlik deur 'n verminderde groei van hierdie weefsel, as gevolg van 'n B tekort, teweeg gebring. Die enigste konstante reaksie van B was 'n negatiewe effek op die Mn-inhoud van al die weefsel wat ontleed is. B het geneig om in die blaarweefsel te akkumuleer oor tyd, maar nie in die stamweefsel nie wat laasgenoemde meer geskik maak vir analise wanneer die fisiologiese ouderdom van plantweefsel onbekend is. Lae B toedieningsvlakke het lae B waardes in die stamweefsel gelewer, maar verhoging van die B-toedieningsvlak het nie 'n ooreenstemmende verhoging in die stamweefsel meegebring nie. Dit kan 'n verkeerde aanduiding gee van beskikbare B aangesien die hoer B-toedieningsvlakke nie 'n verhoging in B-inhoud van stamweefsel veroorsaak het nie. Alhoewel die B-vlakke in die blaarweefsel deur die fisiologiese ouderdom van die weefsel beinvloed is, was die verband tussen B-toediening en die B-inhoud van blaarweefsel beter en het dit 'n beter aanduiding van die beskikbaarheid van B gegee.

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