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Fhatuwani N. Mudau, Ambani R. Mudau, Mpumelelo Nkomo and Wonder Ngezimana

Reserve carbohydrates are critical for herbage yields, productivity as well as management strategies of bush tea (Athrixia phylicoides DC). This study was conducted to evaluate carbohydrate accumulation in response to pruning seasons (summer, autumn, winter, and spring) involving different organs grown under different conditions and to determine mean dry matter production of bush tea. Three separate parallel trials were conducted under wild, field, and glasshouse conditions. Seasons and different growing sites were considered as treatments. Treatments for all controlled trials (field and glasshouse) consisted of seasonal pruning (winter, spring, summer, and autumn). Trials were arranged using a randomized complete block design with 25 single plants as replicates per treatment. Seasonal responses revealed that winter had the highest starch (145.0 mg·g−1) in the stems and reserve carbohydrates (480.6 mg·g−1) in the roots, whereas in the roots sugar (400.6 mg·g−1) was highest in summer. The highest significant root reserve carbohydrates occurred in winter (594.6 mg·g−1) and the lowest in autumn (fall) (313.3 mg·g−1). Bush tea plants pruned during winter had the highest overall reserve carbohydrates in the stem (598.7 mg·g−1). Under glasshouse conditions, the highest dry matter production was observed in December (midsummer) (170 g per plant); while in field-grown plants in the same month dry matter production was 400 g per plant. Therefore, the best time to maximize production of bush tea is during the spring and summer seasons.

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Maedza V. Khathutshelo, Nkomo Mpumelelo, Ngezimana Wonder and Mudau N. Fhatuwani

Bush tea (Athrixia phylicoides DC.) is a herbal beverage and medicinal plant indigenous to South Africa. The aim of the study was to provide the baseline for foliar spray application of micronutrients to enhance the quality of bush tea. A trial was conducted to determine the effect of micronutrients on the quality of bush tea. Four separate trials for boron (B), iron (Fe), zinc (Zn), and copper (Cu) were laid out in a completely randomized block design. Treatments consisted of an unsprayed control and single foliar sprays of B, Fe, Zn, and Cu, with 10 replicates. The levels of each element were unsprayed control, 50 mL·L−1, 100 mL·L−1, and 150 mL·L−1. Parameters recorded were leaf tissue B, Fe, Zn, and Cu, and total polyphenol, total antioxidant, total flavonoids, and total tannin contents. Results from this study demonstrated that foliar application of B did not induce significant response in terms of total polyphenol content after B application. There was a quadratic response for total flavonoids (167 mg·g−1), with most of the total flavonoids reaching maximum at 100 mL·L−1. Foliar application of Fe exhibited a quadratic response, with most of the total polyphenols (45.1 mg·g−1) reaching maximum at 100 mL·L−1. All treatments showed a linear response for total antioxidant, total flavonoids, and total tannin contents. Treatments elicited a quadratic response for total polyphenols (70.6 mg·g−1), total antioxidants (78.3 mg·g−1), total flavonoids (148.9 mg·g−1), and total tannin contents (78.3 mg·g−1) after foliar Zn application, reaching maximum at 100 mL·L−1. Foliar application of essential elements in bush tea led to a significant increase in the Zn, Fe, Cu, and B content; application at 100 mL·L−1 is recommended for improved chemical composition of bush tea. A further trial with treatment combinations is required to determine chemical responses of bush tea.

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Ambani R. Mudau, Mpumelelo M. Nkomo, Puffy Soundy, Hintsa T. Araya, Wonder Ngezimana and Fhatuwani N. Mudau

Spinach (Spinacia oleracea) is a member of the Amaranthaceae family. Baby spinach leaves have a very high respiration rate, thus postharvest quality is affected mostly by tissue decay and the development of off-odors. Thus, this study was conducted to investigate the influence of storage temperature and time on the postharvest quality of baby spinach. Baby spinach leaves were harvested 36 days after planting and subsequently stored at 4 and 22 °C for 0, 2, 4, 6, 8, 10, or 12 days. Thereafter, the leaves were incubated for 72 hours at 40 °C to dry. Minerals, trace elements, total phenols, total carotenoids, flavonoids, and antioxidant activities were measured. Concentration of magnesium (Mg), zinc (Zn), and iron (Fe) were declined after 8 days of storage at 4 °C, while at 22 °C they declined after 2 days of storage. Mg, Zn, and Fe revealed a similar trend with significantly higher carotenoids found up to 6 days in storage at 4 °C, while at 22 °C the carotenoid levels declined after only 2 days. Total phenolic compounds gradually decreased in samples stored at 4 °C. However, samples stored at 22 °C showed a rapid decrease after 4 days. Both total antioxidant activities and vitamin C content showed a similar trend, with the content remaining constant at 4 °C and decreasing after 6 days, whereas the total antioxidant activities and vitamin C for leaves stored at 22 °C decreased immediately after 2 days. Results demonstrated that quality of baby spinach deteriorates as storage time and temperature increase.

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Maedza K. Vuwani, Mpumelelo Nkomo, Wonder Ngezimana, Nokwanda P. Makunga and Fhatuwani N. Mudau

Bush tea (Athrixia phylicoides DC.) is an herbal beverage and medicinal plant indigenous to South Africa. This study evaluated the effects of micronutrients on bush tea quality. Treatments consisted of single applications of zinc (Zn), copper (Cu), boron (Bo), iron (Fe), and magnesium (Mg) at three levels (50, 100, and 150 mL/L) and a combination of all micronutrients. A control treatment with no spray was also included. Tea samples were analyzed using head space solid phase microextraction gas chromatography linked to mass spectrometry (HS-SPME-GC-MS). A significant change in the metabolite profile of bush tea was noted. Five major compounds were identified (>80% identification probability) namely alpha-pinene, beta-pinene, myrcene, beta-caryophyllene, and caryophyllene oxide. A linear relationship between percentage leaf tissues and treatment levels of micronutrients in bush tea was also observed. The liquid chromatography linked to mass spectrometry (LC–MS) showed no significant qualitative difference between the control and the micronutrient treatments. There were significant quantitative differences between the control and treatments applied at 50 and 100 mL/L and the combination (B + Zn + Fe + Cu + Mg) applied at 10 and 20 mL/L. The application of micronutrients did have an influence on the metabolite quantities as has been reported with most secondary metabolite fluctuations caused by plant–environment interactions. Altering the micronutrient application may be a possible solution in achieving commercial agricultural production of this medicinal beverage.