A comparative study of four Malayan ferns, Christensenia aesculifolia (Bl.) Maxon, Tectaria singaporeana (Wall.) Ching, Abacopteris multilineata (Wall.) Ching and Hymenophyllum polyanthos Sw. from shady habitats and another four, Dicranopteris linearis (Burm.) Und., Lygodium scandens (L.) Sw., Blechnum orientate Linn, and Stenochlaena palustris (Burm.) Bedd. from sunlit habitats showed that the total chlorophyll content expressed on a gram fresh weight basis was greater in the shade ferns. There was little difference in the chlorophyll content between the sun and shade ferns when it was expressed on a per unit leaf area basis. The protein and protohaem content was greater in the sun ferns. Measurements of the in vitro photochemical activities of the photosystems I and II in isolated chloroplasts by means of an oxygen electrode showed higher rates in the sun ferns. As determined by spectrophotometric analysis, the photosynthetic cytochrome content from isolated chloroplasts was greater in the sun ferns. The results indicate that the sun ferns have physiological characteristics favouring greater capacity for photosynthesis. Mitochondria isolated from the sun ferns showed faster rates of electron transport using exogenous NADH as substrate.
Plant growth promoting rhizobacteria (PGPR) shows an important role in the sustainable agriculture industry. The increasing demand for crop production with a significant reduction of synthetic chemical fertilizers and pesticides use is a big challenge nowadays. The use of PGPR has been proven to be an environmentally sound way of increasing crop yields by facilitating plant growth through either a direct or indirect mechanism. The mechanisms of PGPR include regulating hormonal and nutritional balance, inducing resistance against plant pathogens, and solubilizing nutrients for easy uptake by plants. In addition, PGPR show synergistic and antagonistic interactions with microorganisms within the rhizosphere and beyond in bulk soil, which indirectly boosts plant growth rate. There are many bacteria species that act as PGPR, described in the literature as successful for improving plant growth. However, there is a gap between the mode of action (mechanism) of the PGPR for plant growth and the role of the PGPR as biofertilizer-thus the importance of nano-encapsulation technology in improving the efficacy of PGPR. Hence, this review bridges the gap mentioned and summarizes the mechanism of PGPR as a biofertilizer for agricultural sustainability.
This study represents the first paper of the effects of growth regulators on the physiochemical and phytochemical properties of the wax apple fruit, a widely cultivated fruit tree in southeast Asia. Net photosynthesis, sucrose phosphate synthase (SPS) activity, peel color, fruit firmness, juice content, pH value, total soluble solids (TSSs), and the sugar acid ratio were all significantly increased in growth regulators (PGRs) treated fruits. The application of gibberellin (GA(3)), naphthalene acetic acid (NAA), and 2,4-dichlorophenoxy acetic acid (2,4-D) significantly reduced titratable acidity and increased total sugar and carbohydrate content compared to the control. The 50 mg/L GA₃, 10 mg/L NAA, and 5 mg/L 2,4-D treatments produced the greatest increases in phenol and flavonoid content; vitamin C content was also higher for these treatments. PGR treatment significantly affected chlorophyll, anthocyanin, and carotene content and produced higher phenylalanine ammonia lyase (PAL) and antioxidant activity levels. There was a positive correlation between peel color and TSS and antioxidant activity and both phenol and flavonoid content and PAL activity and anthocyanin formation. A taste panel assessment was also performed, and the highest scores were given to fruits that had been treated with GA₃ or auxin. The study showed that application of 50 mg/L GA₃, 10 mg/L NAA, and 5 mg/L 2,4-D once a week from bud development to fruit maturation increased the physiochemical and phytochemical properties of wax apple fruits.