The effect of branch number on crown size and biomass accumulation has been reported for many trees, but knowledge about sexual differences in growth and aboveground biomass allocation related to branch number is still limited. Morus alba L. is a dioecious plant of economic importance, and was employed as a model species in our study. Thirty male and 30 female 1-month-old M. alba saplings with single or multiple (five) primary branches were cultivated for one growing season. Sexual differences in gas exchange, morphology, biomass accumulation and allocation, and relationships among morphological and biomass traits were investigated. Branch multiplication significantly increased the total leaf number, total leaf area, total leaf mass, aboveground mass, leaf : stem biomass ratio and specific leaf area at the plant level but decreased net photosynthetic rate (Pn), leaf number, mean single-leaf area, stem length, basal diameter and branch biomass at the branch level. Five-branch male saplings exhibited a significantly higher Pn, total leaf number, total leaf area, total leaf mass and aboveground biomass than did female ones. No such between plant sex differences were found in single-branch saplings. Further, branch number was positively correlated with aboveground mass in male saplings only. Our results demonstrate that branch multiplication might result in sexual differences in morphology and biomass accumulation and male saplings may allocate greater resources than females to aboveground parts for vegetative growth.
Earthworm mucus is rich in nutrients that can initiate the mineralization and humification of organic matter and is of great importance for contaminated soil remediation and sludge reutilization. In this study, six voltage and current combinations were utilized to promote earthworm mucus production (5 V and 6 V at 10, 20 and 30 mA, respectively), to explore the compositional changes of the mucus produced under different electrical stimuli, and to propose the best electrical stimulation group and mucus fraction applicable to soil heavy metal pollution remediation and sludge reutilization. The results showed that the mucus produced by the six electrical stimuli was mainly composed of proteins, amino acids, carbohydrates, fatty acids, and polysaccharides, with small amounts of alcohol, phenol, and ester organic substances. Under different electrical stimuli, each component changed significantly (P < 0.05). pH and conductivity were higher at 6 V 20 mA, total nitrogen and phosphorus contents reached their maximum at 5 V 30 mA, and total potassium at 6 V 10 mA. Protein, amino acids, and carbohydrates were most abundant in the mucus produced at 5 V 10 mA, while trace metal elements reached their lowest values at 5 V 10 mA. Finally, based on principal component analysis and combined with previous studies, it was concluded that the mucus produced at 5 V 10 mA was weakly alkaline, high in amino acids and nutrients and low in trace metal elements, and most suitable for sludge and straw composting experiments, soil remediation and amendment experiments.
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