<p>Циљ&nbsp; овог&nbsp; истраживања&nbsp; је био развој и валидација&nbsp; методе&nbsp; за&nbsp; процену&nbsp; комплексности стехиометријских проблема. Метода&nbsp; за&nbsp; процену&nbsp; комплексности&nbsp; укључује дизајн&nbsp; табеле&nbsp; за&nbsp; процену&nbsp; тежине&nbsp; и интерактивности&nbsp; концепата.&nbsp; Нумерички рејтинг когнитивне комплексности задатака на Тесту&nbsp; одређен&nbsp; је&nbsp; комбиновањем&nbsp; Табеле&nbsp; са методом Кнауса и сарадника. Метода за процену<br />комплексности&nbsp; стехиометријских&nbsp; проблемских задатака&nbsp; је&nbsp; валидирана&nbsp; статистички,корелационом&nbsp; анализом&nbsp; односа ученичког постигнућа и нумеричког рејтинга когнитивне комплексности&nbsp; проблема, као и односом уложеног&nbsp; менталног&nbsp; напора&nbsp; и&nbsp; процењене комплексности. При томе су добијене изузетно високе&nbsp; вредности&nbsp; корелационих коефицијената. Поред&nbsp; статистичке&nbsp; валидације&nbsp; Метода&nbsp; је подвргнута&nbsp; и&nbsp; валидацији&nbsp; применом&nbsp; Теорије простора знања. Применом предложене Методе конструисан&nbsp; је&nbsp; очекивани&nbsp; простор знања, а применом&nbsp; кориговане&nbsp; и&nbsp; минимизиране&nbsp; IITA конструисaн је реални простор знања из ученичких&nbsp; постигнућа&nbsp; на&nbsp; тесту.&nbsp;&nbsp;&nbsp; Простори знања су упоређен применом теорије графова. Очекивани&nbsp; и&nbsp; реални&nbsp; простор&nbsp; знања&nbsp; садрже велики&nbsp; број&nbsp; истих&nbsp; релација&nbsp; претпостављања, чиме&nbsp; је&nbsp; додатно&nbsp; потврђена&nbsp; валидност&nbsp; Методе.<br />Примена КСТ у валидацији Методе омогућила једа се увиде фине разлике између очекиваног и&nbsp; реалног&nbsp; простора&nbsp; знања&nbsp; на&nbsp; основу&nbsp; чега&nbsp; је указано&nbsp; на&nbsp; могућности&nbsp; даљег&nbsp; побољшања наставе стехиометрије.</p> / <p>Cilj&nbsp; ovog&nbsp; istraživanja&nbsp; je bio razvoj i validacija&nbsp; metode&nbsp; za&nbsp; procenu&nbsp; kompleksnosti stehiometrijskih problema. Metoda&nbsp; za&nbsp; procenu&nbsp; kompleksnosti&nbsp; uključuje dizajn&nbsp; tabele&nbsp; za&nbsp; procenu&nbsp; težine&nbsp; i interaktivnosti&nbsp; koncepata.&nbsp; Numerički rejting kognitivne kompleksnosti zadataka na Testu&nbsp; određen&nbsp; je&nbsp; kombinovanjem&nbsp; Tabele&nbsp; sa metodom Knausa i saradnika. Metoda za procenu<br />kompleksnosti&nbsp; stehiometrijskih&nbsp; problemskih zadataka&nbsp; je&nbsp; validirana&nbsp; statistički,korelacionom&nbsp; analizom&nbsp; odnosa učeničkog postignuća i numeričkog rejtinga kognitivne kompleksnosti&nbsp; problema, kao i odnosom uloženog&nbsp; mentalnog&nbsp; napora&nbsp; i&nbsp; procenjene kompleksnosti. Pri tome su dobijene izuzetno visoke&nbsp; vrednosti&nbsp; korelacionih koeficijenata. Pored&nbsp; statističke&nbsp; validacije&nbsp; Metoda&nbsp; je podvrgnuta&nbsp; i&nbsp; validaciji&nbsp; primenom&nbsp; Teorije prostora znanja. Primenom predložene Metode konstruisan&nbsp; je&nbsp; očekivani&nbsp; prostor znanja, a primenom&nbsp; korigovane&nbsp; i&nbsp; minimizirane&nbsp; IITA konstruisan je realni prostor znanja iz učeničkih&nbsp; postignuća&nbsp; na&nbsp; testu.&nbsp;&nbsp;&nbsp; Prostori znanja su upoređen primenom teorije grafova. Očekivani&nbsp; i&nbsp; realni&nbsp; prostor&nbsp; znanja&nbsp; sadrže veliki&nbsp; broj&nbsp; istih&nbsp; relacija&nbsp; pretpostavljanja, čime&nbsp; je&nbsp; dodatno&nbsp; potvrđena&nbsp; validnost&nbsp; Metode.<br />Primena KST u validaciji Metode omogućila jeda se uvide fine razlike između očekivanog i&nbsp; realnog&nbsp; prostora&nbsp; znanja&nbsp; na&nbsp; osnovu&nbsp; čega&nbsp; je ukazano&nbsp; na&nbsp; mogućnosti&nbsp; daljeg&nbsp; poboljšanja nastave stehiometrije.</p> / <p>The&nbsp; main goal&nbsp; of&nbsp; this&nbsp; dissertation&nbsp; was&nbsp; to develop and validate the Method for estimation of the complexity of stoichiometric problems. The&nbsp; Method&nbsp; for&nbsp;&nbsp; assessment&nbsp; of&nbsp; complexity involves the design of a table for assessment of difficulty and interactivity of the concepts. The numerical rating of the cognitive complexity of tasks on the Test is determined by combining the Table with the Knaus et al. (2011) method. Method&nbsp; for&nbsp; estimation&nbsp; of&nbsp; the&nbsp; complexity&nbsp; of stoichiometric&nbsp; problems&nbsp; is validated&nbsp; by&nbsp; a statistically&nbsp; significant correlation analysis between students&#39; performances and cognitive complexity,&nbsp; as&nbsp; well&nbsp; as&nbsp; between&nbsp; students&#39;evaluation &nbsp; of&nbsp; invested&nbsp; mental&nbsp; effort&nbsp; and cognitive&nbsp; complexity. In doing so, extremely high values&nbsp; of&nbsp; correlation&nbsp; coefficients&nbsp; were obtained.&nbsp; In addition to statistical validation,&nbsp; the Method was&nbsp; subjected&nbsp; to&nbsp; validation&nbsp; using&nbsp; the Knowledge Space Theory. Using the proposed Method,&nbsp; the&nbsp; expected&nbsp; knowledge&nbsp; space&nbsp; was constructed, and by applying the corrected and minimized&nbsp; IITA,&nbsp; a&nbsp; real&nbsp; knowledge&nbsp; space from student&nbsp; achievement&nbsp; on&nbsp; the&nbsp; test&nbsp; was constructed. Knowledge&nbsp; spaces&nbsp; are&nbsp; compared using&nbsp; graph difference.&nbsp; The&nbsp; expected&nbsp; and&nbsp; real&nbsp; knowledge space&nbsp; contained&nbsp; a&nbsp; large&nbsp; number&nbsp; of&nbsp; the&nbsp; same surmise relations, which additionally confirms the validity of Method. Differences between theknowledge&nbsp; space&nbsp; pointed&nbsp; to&nbsp; some&nbsp; facts&nbsp; that teachers often do not see with their students.The&nbsp; application&nbsp; of&nbsp; KST&nbsp; in&nbsp; the&nbsp; Method validation pointed out the fine differencesbetween&nbsp; the&nbsp; expected&nbsp; and&nbsp; real&nbsp; knowledge space,&nbsp; indicating&nbsp; possibilities&nbsp; for&nbsp; further improvement of stoichiometry teaching.</p>

Student Number : 0413249D - MSc research report - Faculty of Science / Cassava is one of the most important staple crops in the world and is consumed by over 700 million people around the globe and is a profitable product commercially due to the high starch content of its tubers. One of the future aims is to produce cassava that is high yielding, resistant to cassava mosaic geminiviruses (CMGs) and high in starch content. To be able to achieve commercially attractive cassava varieties, research need to be carried out to investigate the virus resistance status of different cassava cultivars, which can later be used in the future breeding programme. In South Africa, cassava is used for commercial starch manufacturing purposes, as a cash crop and a food source by small-scale farmers. Cassava Mosaic Disease (CMD) is having a negative impact on yield of the crop globally and therefore dropping profitability of cassava on a commercial scale. The aims of this research were to propagate thirteen cassava cultivars and then to test them for virus susceptibility or resistance. Eleven cassava cultivars received from the International Institute of Tropical Agriculture (IITA) were tested for resistance or susceptibility against South African cassava mosaic virus (SACMV). Two local, commercial cultivars T200 and T400, were tested for East African cassava mosaic virus (EACMV) and African cassava mosaic virus (ACMV) resistance. Cassava cultivars were successfully propagated in vitro and thereafter transferred into soil and acclimatized to adapt to environmental conditions. When the plantlets were three weeks old, the plantlets were infected with cassava mosaic viruses. Plants were infected with SACMV via Agrobacterium-mediated transfer and infectious EACMV and ACMV monomers were used to biolistically bombard the plantlets. Resistance/susceptibility results of seven of the thirteen cultivars were obtained with SACMV, these cultivars being T200 (susceptible), T400 (susceptible), TME3 (highly resistant), I30572 (susceptible), I420251 (highly susceptible), I60506 (susceptible) and TMS60444 (susceptible). Due to destruction by fungal gnats eating the roots of the plants, acclimatization of the remaining six cultivars was not possible. Also, due to the nature of the biolistic equipment, infection of the cultivars with EACMV and ACMV was not achieved as the plantlets were not robust enough to survive the pressure.