How Do Different Watering Regimes Affect the Growth,Chlorophyll Fluorescence,Phytohormone, and Phenolic Acid Content of Greenhouse-Grown Ceratotheca triloba?

We evaluated the effect of different watering regimes on the growth, chlorophyll fluorescence, phytohormones, and phenolic acids in Ceratotheca triloba (Bernh.) Hook.f., a commonly consumed African indigenous leafy vegetable. The study was conducted in the greenhouse under different watering regimes [seven (daily); three (thrice); two (twice); one (once) day(s) per week] for a period of 2 and 4-months. In each pot (7.5 cm diameter; 150 ml volume), 50 ml of water was applied per treatment. At the end of the experiment, plant growth, chlorophyll fluorescence, phytohormones, and phenolic acids were determined. A decrease in water availability resulted in a consistent decline in plant growth after a 4-month growth period. The severity of reduced water availability was more noticeable in plants watered once a week with a 1.4-fold reduction in growth and quantum efficiency of PSII (Fv/Fm) value of 0.80. The significant decline in growth and chlorophyll fluorescence was probably due to the increased production of abscisic acid (ABA) and cytokinin (CK) content together with the detected phytohormones in plants with restricted water supply. Furthermore, plants watered once a week had a trade-off between growth and phenolic acid production, with significantly higher (threefolds) concentrations of vanillic, ferulic, caffeic, and 4-coumaric acids in 4-month-old plants. Even though C. triloba grew best in well-watered soil, the plant had the potential to adapt and survive in soils with limited water supply for longer periods of growth. These findings suggest that regulation of phytohormones and phenolic acids played an important role in improving the growth of C. triloba under limited water conditions.

     

Effect of vermicompost leachate in <Emphasis Type="Italic">Ceratotheca triloba</Emphasis> under nutrient deficiency

Ceratotheca triloba (Bernh.) Hook.f. commonly known as an African foxglove is an indigenous plant which occurs in most parts of South Africa. The species is commonly consumed as a leafy vegetable and utilized for its medicinal properties. Although the high nutritional value of the species and medicinal properties are well documented, information related to critical aspect of cultivation is currently limited. Therefore, this study aimed to evaluate the effect of vermicompost leachate (VCL) on growth, nutritional, phytochemical, and antioxidant levels in C. triloba at different growth stages under nutrient-deficient conditions. After in vitro germination, seedlings were grown in the greenhouse for 2 and 4 months under nitrogen (–N); phosphorus (–P); and potassium (–K) deficiency conditions, and were treated with VCL. Vermicompost leachate did not improve the growth of C. triloba plants under the nutrient-deficient conditions. Although –N-deficient plants with or without VCL caused a decline in growth parameters, they significantly enhanced phytochemicals in 2-month-old plants. In most cases, the application of VCL to –P- and –K-deficient plants improved the photosynthetic pigments, protein, and phenolic, as well as flavonoid accumulation. Harvesting time was also found to play a crucial role in the accumulation of evaluated parameters in nutrient-deprived plants. From these findings, it can be deduced that VCL has a potential to minimize the effect of nutrient deficiency especially under –P and –K deficiency in C. triloba plants.     

A novel inhibitor of cytokinin degradation (INCYDE) influences the biochemical parameters and photosynthetic apparatus in NaCl-stressed tomato plants

The effect of 2-chloro-6-(3-methoxyphenyl)aminopurine [inhibitor of cytokinin degradation (INCYDE)] at 10 nM on growth, biochemical and photosynthetic efficiency in sodium chloride (NaCl)-stressed (75, 100 and 150 mM) tomato plants was investigated. NaCl-induced decline in plant vigor index was slightly reversed by both drenching and foliar application of INCYDE. Foliar application of INCYDE significantly increased the flower number in the control and 75 mM NaCl-supplemented plants, while drenching was more effective in 150 mM NaCl-stressed plants. Antioxidant enzymes (peroxidase, catalase and superoxide dismutase) were enhanced in the presence of INCYDE in the control and NaCl-stressed plants. Higher concentration of malondialdehyde (MDA) associated with oxidative (lipid peroxidation) damage in leaf tissue which was evident in the presence of NaCl stress was significantly attenuated with the drenching and foliar application of INCYDE. Regardless of NaCl concentration, application of INCYDE had no significant influence on maximum quantum efficiency of photosystem II. However, the reduced quantum yield of photosystem II and coefficient of photochemical quenching under continuous illumination with actinic light at four intensities (264, 488, 800 and 1,200 µmol m^?2 s^?1) in NaCl-stressed (100 and 150 mM) tomato plants were significantly alleviated by drenching application with INCYDE. Non-photochemical quenching of the singlet excited state of chlorophyll a and relative electron transfer rate were generally higher in INCYDE-treated plants than in the controls. From an agricultural perspective, these findings indicate the potential of INCYDE in protecting plants against NaCl stress and the possibility of enhanced productivity.     

Plant growth regulator induced phytochemical and antioxidant variations in micropropagated and acclimatized Eucomis autumnalis subspecies autumnalis (Asparagaceae)

Eucomis species is a valuable plant with both medicinal and horticultural potential. The current study evaluated the role of plant growth regulator (PGR) on growth, phytochemicals, and antioxidant activity in Eucomis autumnalis subspecies autumnalis. Five cytokinins including topolins and benzyladenine (BA) at 2 µM in combination with varying (0–15 µM) concentrations of naphthalene acetic acid (NAA) were tested. In vitro regenerants were acclimatized in the greenhouse for 4 months. Highest number of shoots (9 shoots/explant) was observed with 15 µM NAA alone or when combined with BA. Acclimatized plants derived from the 15 µM NAA treatment had the highest number of roots, largest leaf area and biggest bulbs. While applied PGRs increased the iridoids and condensed tannins in the in vitro regenerants, total phenolics and flavonoids were higher in the PGR-free treatment. Among the in vitro regenerants, 5 µM NAA and 2 µM BA treatments produced the best antioxidant activity in the DPPH (55 %) and beta-carotene (88 %) test systems, respectively. A remarkable carry-over effect of the PGR was conspicuous in the phytochemical levels and antioxidant activity of the 4-month-old plants. In addition to the optimized micropropagation protocols, the current findings present a promising potential for manipulating the type and concentration of applied PGRs to improve phytochemical production and hence medicinal value in E. autumnalis subspecies autumnalis.     

Physiological and phytochemical responses of three nutrient-stressed bulbous plants subjected to vermicompost leachate treatment

The role of vermicompost leachate (VCL) on growth, photosynthetic pigments, phytochemical content and the bioactivities of three bulbous (Eucomis autumnalis, Tulbaghia ludwigiana and Tulbaghia violacea) plants with medicinal and horticultural potential under nutrient-stressed conditions was evaluated. After 15 weeks, the nutrient-stressed plants were harvested and growth parameters were recorded. Spectrophotometric methods were used to quantify the photosynthetic and phytochemical contents. Harvested plant materials were extracted with 50 % methanol and subjected to antioxidant, acetylcholinesterase inhibitory (AChEI) and antifungal bioassays to elucidate the effect of the applied VCL under nutrient stress. While VCL did not significantly enhance growth of the three species, it significantly increased photosynthetic pigment content in 50 % Hoagland’s-treated Eucomis autumnalis and in phosphorus-deficient Tulbaghia ludwigiana. Among the quantified phytochemicals, the most promising finding was the significant increase in condensed tannin and iridoid contents in VCL-supplemented-nutrient-stressed Tulbaghia violacea. Better antioxidant (Eucomis autumnalis) and AChEI (Eucomis autumnalis, Tulbaghia violacea) activities were detected when VCL was applied under nutrient stress. The current findings indicate that the application of VCL holds potential in cultivation of plants under nutrient-stressed conditions.     

Changes in phytochemical content and pharmacological activities of three <Emphasis Type="Italic">Chlorella</Emphasis> strains grown in different nitrogen conditions

The phytochemical content and biological activity of three Chlorella strains cultured in low (35 mg L^?1) or high (700 mg L^?1) nitrogen (N) and harvested on days 5 and 10 were evaluated. High N resulted in a higher biomass in Chlorella MACC 438 and MACC 452 while MACC 555 produced a higher biomass in low N. MACC 555 (low N/day 5) had the highest phenolic content, and MACC 438 in low N/day 5 and high N/day 5 accumulated the highest flavonoids and condensed tannins, respectively. Iridoids were most abundant in MACC 452 on low N/day 10. Harvest time had the greatest effect on the phytochemical content with phenolics, flavonoids, and condensed tannins decreasing over time and iridoids increasing in low N and decreasing in high N conditions. Extracts were more active in β-carotene-linoleic acid model compared to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Most extracts had good antimicrobial activity. Extracts became less potent over time in the antioxidant, acetylcholinesterase inhibitory (AChE), and antimicrobial assays when growing in low N and more potent in the antioxidant and AChE assays when grown in high N. Thus, phytochemical content and biological activities of the three Chlorella strains were affected by N levels, harvest time, and strain.     

Effects of cold acclimation on the activity levels of creatine kinase, lactate dehydrogenase and lactate dehydrogenase isoenzymes in various tissues of the rat.

The effects of cold acclimation on the activity levels of creatine kinase, lactate dehydrogenase and lactate dehydrogenase isoenzymes in various tissues/ organs of the rat (Rattus norvegicus) were investigated. Male Sprague-Dawley rats were divided into two groups. One group was housed at 4+/-1 degrees C (experimental group) and the other at 24+/-1 degrees C (control group) for six months. The rats were housed in single cages and had access to food and water ad libitum. The tissues/organs investigated were heart, liver, lung, kidney, gastrocnemius muscle and interscapular brown adipose tissue as well as serum. With the exception of lung, (which showed a decrease of 24%) total creatine kinase activity levels were significantly increased (P< 0.05) in all the tissues/organs investigated (17-51%) as well as serum (34%), in cold acclimated animals. Cold acclimation also resulted in significantly increased (P< 0.05) activity levels of lactate dehydrogenase in all the tissues/organs investigated (14-24%) as well as serum (35%). Cold exposure resulted in an increase of the activity levels of all the detectable isoenzymes of lactate dehydrogenase, although not always significant, in all the tissues/organs investigated as well as serum. The M(4)tetramer of lactate dehydrogenase was the only detectable isoenzyme in serum.     

Regulating the regulators: responses of four plant growth regulators during clonal propagation of <Emphasis Type="Italic">Lachenalia montana</Emphasis>

Geraniol, the precursor of terpenoid indole alkaloids can be converted to the 10-hydroxy geraniol by the function of geraniol 10-hydroxylase. In our study, for the first time, a full-length cytochrome P450 monooxygenase (P450) geraniol 10-hydroxylase (PgCYP76C9) cDNA was isolated and characterized from Panax ginseng Meyer. The gene has an open reading frame (ORF) of 1503 base pairs and encodes a precursor protein of 501 amino acids residues. The calculated molecular mass of the protein is approximately 56.3 kDa with a predicated isoelectric point of 8.45. Amino acid identities between PgG10H and other P450s of the CYP76 family in the database had revealed that the deduced amino acid of PgG10H sharing a higher sequence homology with geraniol 10-hydroxylase-like proteins encoded by Cinchona calisaya and Lonicera japonica. We implemented a molecular modeling method to evaluate the possible interaction of geraniol with PgG10H active site. Our finding showed that the geraniol was the potential ligand for PgG10H in P. ginseng. Expression of PgG10H gene was tissue-regulated and showed high expression in 3-year-old ginseng flowers and roots. Expression of PgG10H was differentially induced in ginseng, not only during Pseudomonas syringae infection and wounding but also after exposure to methyl jasmonate and salt stress. Furthermore, overexpression of the newly identified ginseng geraniol 10-hydroxylase P450 gene in Arabidopsis caused terpenoid indole alkaloid dihydrositsirikine production and also conferred enhanced resistance to P. syringae.     

Effects of chronic cold exposure on the activities of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in rat tissues (Rattus norvegicus)

The effects of cold acclimation on the activity levels of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in various tissues of the rat (Rattus norvegicus) were investigated. One group was individually housed at 4 +/- 1 degrees C and the other at 24 +/- 1 degrees C for 6 months. Chronic cold acclimation resulted in significantly (P < 0.05) increased cytochrome c oxidase activity levels in liver, kidney, heart, interscapular brown adipose tissue and gastrocnemius muscle. The activity of glutathione peroxidase was significantly (P < 0.05) elevated in liver, interscapular brown adipose tissue, lung and muscle, whereas glutathione reductase was only significantly (P < 0.05) elevated in interscapular brown adipose tissue as a result of chronic cold exposure. The results obtained are possibly indicative of a positive compensatory response against the increased production of oxygen derived radicals as a result of chronic cold exposure.