The impact of paraffin on germination of selected crop seeds and its possible pest repellent action

Kadende, John Sembeba (2014-12)

Thesis (MScAgric)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Paraffin, also called kerosene is used by small-scale soya bean farmers in some parts of Africa as a pest repellent. The repellent action is claimed to be effective against parasites during seed germination and development of the seedlings. Seeds are immersed in commercial paraffin for a few seconds and sown in the soil immediately. This method raised some questions about possible negative effects on the seed after the imbibition process but also on humans and animals consuming the plants and seeds. Experiments were designed to investigate whether this practice would have negative effects on seed germination and vigour of the resulting seedlings of seven selected crop species. A trial was also carried out to test the effectiveness of paraffin as a pest repellent on canola in a field situation. The collected data were analyzed using STATISTICA, software version 11. Wherever the experiments showed significant interaction or differences within main factors, the means were separated making use of Fischer’s LSD post-hoc analysis at p = 0.05. The first series of experiments was done in the laboratory. It was carried out on seeds of seven crop species: canola (Brassica napus L.), common beans (Phaseolus vulgaris L.), ground nuts (Arachis hypogea L.), maize (Zea mays L.), soya bean (Glycine max L.), sunflower (Helianthus annuus L.) and wheat (Triticum aestivum L.). In the germination trial, seeds were subjected to a 7X5X4 factorial design treatment with factors Crop species (CS) (see above), Paraffin concentration (PC) (0, 25, 50, 75 and 100% of commercial paraffin diluted with distilled water) and Time of immersion (TOI) (1, 5, 10, and 30 minutes). Treatments were repeated four times. After immersion seeds were dried with water absorbent paper and immediately germinated in 90 mm diameter petri dishes containing two filter papers and 5 ml of distilled water. Germination tests included 10 seeds per replicate and were incubated at a constant temperature of 20°C under dark conditions in an incubator. Findings showed that canola, sunflower and soya bean are paraffin tolerant (>70 % germination), wheat and groundnuts are less tolerant (30% – 70% germination) and beans and maize are intolerant (< 30 % germination). The paraffin had a negative influence on the rate of germination but there were no statistically significant differences between the 25% to 100% paraffin concentrations. Measurements of the quantity of water and of paraffin absorbed were done after seeds of the seven crop species were immersed in 0, 25, 50, 75 and 100% paraffin concentrations for 30 minutes. Beans absorbed more water at 100% water and more paraffin at 25% paraffin than the other crop species. The paraffin uptake decreased with the increase of paraffin concentration while water uptake increased with the increase in water percentage. In both cases canola had the lowest uptake. Differential uptake of water and paraffin did not explain the results of the germination test. Seeds of the seven crop species immersed in different paraffin concentrations (0, 25, 50, 75 and 100%) for thirty minutes were dried and then soaked in distilled water for 20 hours. The electrical conductivity (EC) of the liquid was determined by means of an EC meter after 20 hours of soaking. This was done to investigate whether paraffin treatment influenced leaking of electrolytes, which would indicate damage to the cell membranes in the seed. Results showed that sunflower leaked more electrolytes than any other seed, while wheat and maize had lower electrolyte leakage than the other species. This showed that the negative effect of paraffin on the germination of some crop species was unlikely to be due to membrane damage because sunflower seeds that leaked most electrolytes had a high germination percentage while the maize and wheat seeds that leaked little electrolytes, had poor germination after paraffin treatments. The second experiment was conducted in a glasshouse. Seeds of the seven crop species were subjected to the same PC and TOI treatments as described in the germination experiment above but instead of being placed in an incubator to germinate, they were planted in 8cm x 8 cm plastic pots (10 seeds in each) in coarse sand in a glasshouse that was running at approximately 20ºC. The establishment of the seedlings was monitored daily in the glasshouse. The final percentage of establishment was calculated. Three weeks after planting, the seedlings were thinned to one plant per pot. The mean root and stem lengths as well as dry mass of the seedlings was recorded when the seedlings were thinned. The one plant per pot that was retained was harvested six weeks after establishment. Root and stem length and dry mass were determined. Establishment percentage and tolerance indices were calculated. Maize and beans showed the lowest establishment percentages and sunflower scored the highest establishment percentage after treatment with paraffin. The root and stem lengths of the crops were generally unaffected by paraffin treatments. In terms of dry mass paraffin had a significant negative effect on groundnut at three weeks but at six weeks no effect of paraffin on any of the vegetative growth parameters could be observed. The third experiment was run in the microscope laboratory. A test using a confocal and fluorescence microscope was carried out to determine if residues of paraffin could be found in germinating soya bean seeds and seedlings. Specimens collected from the germinating soya bean seed and seedlings were mounted on the fluorescent microscope and stained with a solution of 100 μg.ml-1 Nile Red and observed with LD Plan-Neofluar 60X/0.6. Results showed that paraffin did penetrate the soya bean seed and was translocated within the plant system (endodermis) as the plant grows. The concentrations of paraffin in the tissue were however quite low. The fourth experiment was run on the Langgewens Experimental Farm near Moorreesburg in the Western Cape Province. Forty blocks were spatially grouped into two separate groups. Twenty blocks received the five paraffin treatments replicated four times and the other twenty blocks received the five water treatments also replicated four times. Within each group the treatments were allocated randomly to the plots. The experimental design was a 2X5 Factorial experiment with factors Treatment liquid (distilled water and paraffin) and Time of immersion (0, 1, 5, 10 and 30 minutes) replicated four times. No pesticides were applied to the canola crop. Stand density, leaf area and dry mass were recorded at the first harvest at 12 weeks, and then dry mass was determined at 21weeks. Final yield was determined after 27 weeks when the plots were harvested by means of a combine plot harvester. The stand density, leaf area and dry mass were significantly increased by paraffin treatments at the time of the first harvest. After 21 weeks paraffin treatment had no significant effect on the dry mass production of the canola and the same was true of the final seed yield. . Even though there was no serious attack by pests, the little feeding damage that occurred in the water treated plots and not in the paraffin treated plots, indicate that paraffin may have a repellent effect. Paraffin had no negative effects whatsoever on the growth and yield of canola in this experiment. This study indicates that different crops react differently to seed treatment with paraffin. The results of the fourth experiment indicate that paraffin might be used as pest repellent on certain selected crops but more research is needed on the subject.

AFRIKAANSE OPSOMMING: Paraffien, ook genoem keroseen, word deur kleinskaalse boere in sekere dele van Afrika gebruik as ‘n pesafweermiddel. Dit word beweer dat die afweeraksie suksesvol is teen parasiete tydens saadontkieming en vroeë saailinggroei. Saad word in kommersiële paraffien gedoop vir ‘n paar sekondes en dan onmiddelik daarna geplant. Die metode skep vrae oor die moontlike negatiewe gevolge op die saad na die imbiberingsproses maar ook op mense en diere wat die plante en sade benut. Eksperimente is beplan om vas te stel of die praktyk negatiewe gevolge op die saadontkieming en groeikragtigheid van die daaropvolgende saailinge van sewe geselekteerde gewasspesies sal hê. ‘n Eksperiment is ook uitgevoer om die effektiwiteit van paraffien as pesafweermiddel op kanola in ‘n veldsituasie te toets. Die data wat ingesamel is is ontleed deur gebruik te maak van STATISTICA, sagteware, uitgawe 11. Waar betekenisvolle interaksies of verskille binne hooffaktore voorgekom het, is die gemiddeldes geskei deur middel van Fischer se LSD post-hoc ontleding by p = 0.05. Die eerste reeks eksperimente is uitgevoer in ‘n laboratorium. Dit is uitgevoer op sade van sewe gewasspesies naamlik . kanola (Brassica napus L.), gewone bone (Phaseolus vulgaris L.), grondbone (Arachis hypogea L.), mielies (Zea mays L.), sojabone (Glycine max L.), sonneblom (Helianthus annuus L.) en koring (Triticum aestivum L.). In die ontkiemingsproef is die sade onderwerp aan ‘n 7X5X4 ewekansige blokontwerp wat faktoriaal gerangskik is met faktore Gewasspesies (CS) (sien hierbo), Paraffien konsentrasie (PC) (0, 25, 50, 75 en 100% van kommersiële paraffien verdun met gedistilleerde water) en Tyd van indompeling (TOI) (1, 5, 10, en 30 minute). Behandelings is vier keer herhaal. Na indompeling is die sade met waterabsorberende papier gedroog en onmiddelik daarna in 90 mm deursneë petribakkies wat twee filtreerpapiere en 5 ml gedistilleerde water bevat het, ontkiem. Tien sade per petribakkie is gebruik en die petribakkies is geïnkubeer by ‘n konstante temperatuur van 20ºC in die donker in ‘n inkubasiekas. Resultate het getoon dat kanola, sonneblom en sojaboon bestand is teen paraffienbehandelings (>70% ontkieming), koring en grondboon is minder bestand (30-70% ontkieming) en mielies en gewone bone is sensitief vir paraffienbehandeling (<30% ontkieming). Die paraffien het oor die algemeen ‘n negatiewe effek op ontkiemingstempo gehad maar daar was geen statisties betekenisvolle verskille tussen die 25% en 100% paraffienbehandelings nie. Die hoeveelheid water en paraffien wat opgeneem is deur sade van die sewe gewasspesies nadat dit in paraffienkonsentrasies van 0, 25, 50, 75 en 100% ingedompel is vir 30 minute, is bepaal. Gewone bone het meer water by die 100% water behandeling en meer paraffien by die 25% paraffien behandeling opgeneem as die ander spesies. Die paraffienopname het afgeneem met toename in paraffienkonsentrasie terwyl wateropname toegeneem het met toenemende waterkonsentrasies. Beide in geval van wateropname en paraffienopname het kanola die minste water opgeneem. Differensiële opname van water en paraffien het nie die resultate van die ontkiemingstoets verklaar nie. Sade van die sewe gewasspesies is in verskillende paraffienkonsentrasies (0, 25, 50, 75 en 100%) gedompel vir 30 minute, gedroog en daarna in gedistilleerde water geweek vir 20 uur. Aan die einde van die 20 uur wekingsperiode is die elektriese konduktiwiteit (EC) van die wekingsvloeistof bepaal deur middel van ‘n EC meter. Dit is gedoen om vas te stel of paraffienbehandeling die uitlek van elektroliete vanuit die saad, wat ‘n aanduiding van beskadigde selmembrane van die saad kan wees, beïnvloed. Resultate het aangedui dat sonneblom die meeste elektroliete vrygestel het en koring en mielies die minste. Dit dui aan dat die negatiewe invloed van paraffien op sommige gewasspesies waarskynlik nie deur membraanbeskadiging veroorsaak is nie omdat sonneblom, wat die meeste elektroliete vrygestel het, die hoogste ontkiemingspersentasie na behandeling met praffien gehad het terwyl mielies en koring, wat die minste elektroliete vrygestel het, baie swak ontkieming gehad het na paraffienbehandeling. Die tweede eksperiment is in ‘n glashuis uitgevoer. Sade van die sewe gewasspesies is onderwerp aan dieselfde paraffienkonsentrasies en tye van indompeling as in die ontkiemingseksperiment hierbo maar in plaas van om die sade in ‘n inkubasiekas te ontkiem, is dit in 8 cm x 8 cm plastiekpotte wat gevul is met growwe sand geplant (10 sade per pot) in ‘n glashuis wat by ‘n konstante temperatuur van ongeveer 20ºC geloop het. Die vestiging van die saailinge in die glashuis is daagliks gemonitor en die finale persentasie van vestiging is bereken. Drie weke na plant is die saailinge uitgedun sodat een per pot oorgebly het. Die uitgedunde saailinge se gemiddelde wortel- en stamlengtes is bepaal asook die gemiddelde droëmassas. Die een plant wat per pot oorgebly het is na ses weke ge-oes en weer is wortel- en stamlengtes bepaal asook die droëmassas. Vestigingspersentasies en toleransie indekse is bereken. Mielies en gewone bone het die laagste vestigingspersentasies getoon en sonneblom die hoogste nadat die gewasse met paraffien behandel is. Die wortel- en stamlengtes van die gewasse was oor die algemeen nie deur paraffienbehandelings beïnvloed nie. In terme van droëmassa het paraffien ‘n negatiewe effek op grondbone gehad drie weke na plant maar na ses weke kon geen invloed van paraffienbehandelings op enige van die vegetatiewe groeiparameters waargeneem word nie. Die derde eksperiment is in ‘n mikroskooplaboratorium uitgevoer. ‘n Konfokale en fluoreserende mikroskoop is gebruik om te bepaal of oorblyfsels van paraffien gevind kan word in ontkiemende sojaboonsade en saailinge. Monsters wat geneem is van die ontkiemende sojaboonsade saailinge is gemonteer op die fluoreserende mikroskoop en gekleur met ‘n oplossing van 100 μg.ml-1 Nile Red oplossing en ge-evalueer met LD Plan-Neofluar 60X/0.6. Resultate het getoon dat paraffien wel die sojaboonsaad kon infiltreer en dat dit ook in die saailinge se endodermis vervoer kon word en opspoorbaar was. Die konsentrasies van paraffien in die weefsel was egter laag. Die vierde eksperiment is uitgevoer op die Langgewens Proefplaas naby Moorreesburg in die Wes-Kaap Provinsie. Veertig blokke is ruimtelik in twee groepe van twintig elk grangskik. Twintig blokke het die vyf paraffienbehandelings ontvang en twintig die vyf gedistilleerde waterbehandelings. Die behandelings is vier keer herhaal. Binne elke blok is die behandelings ewekansig toegeken aan persele. Die proefontwerp was ‘n 2X5 ewekansige geneste blokontwerp (split plot) wat faktoriaal gerangskik is met faktore Behandelingsvloeistof (gedistilleerde water en paraffien) en indompelingstyd (0, 1, 5, 10 and 30 minute). Geen insekdoders is op die kanola toegedien nie. Plantdigtheid, blaaroppervlakte en droëmassa is bepaal tydens die eerste monsterneming 12 weke na plant en daarna is slegs droëmassa bepaal na 21 weke. Na 27 weke is finale oesopbrengs bepaal deur die persele met ‘n perseelstroper te stroop. Plantdigtheid, blaaroppervlakte en droëmassa is betekenisvol verhoog deur paraffienbehandelings na 12 weke. Na 21 weke het die paraffienbehandelings egter geen betekenisvolle invloed op die droëmassa van die plante gehad nie en daar was ook nie verskille ten opsigte van finale oesopbrengs nie. Alhoewel daar nie ernstige insekskade waargeneem is nie, was dit tog duidelik dat die bietjie vreetskade wat in die waterbehandelings voorgekom het, nie in die paraffienbehandelings voorgekom het nie. Dit dui aan dat die paraffien moontlik ‘n afwerende invloed gehad het. Paraffien het geen negatiewe invloed enigsins gehad op die groei en produksie van kanola in hierdie eksperiment nie. Hierdie studie dui aan dat verskillende gewasse verskillend reageer op saadbehandeling met paraffien. Die resultate van die vierde eksperiment dui aan dat paraffien moontlik as ‘n pesafweermiddel op sekere geselekteerde gewasse gebruik kan word maar meer navorsing word benodig op die onderwerp.

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