Growth Dilatory Effects of PEG and Sucrose on Geranium wallichianum: An In Vitro Approach for Conservation

Abstract

The medicinal herb Geranium wallichianum belongs to the family Geraniaceae. The East Asian Himalayas are its primary habitat. Overexploitation and overharvesting pose a threat to this plant, given its extensive ethnomedical utilization in the community. In Pakistan, its population has already declined by over 75%. Given its critical medicinal importance, urgent conservation efforts are needed to prevent extinction. The aim of the current research was to determine the effectiveness of sucrose and polyethylene glycol (PEG) in decelerating the growth of this medicinally important species. Nodal segments were utilized as explant with varying levels of polyethylene glycol (PEG) (0.5% and 1.5%) and sucrose (4% and 8%) as treatments on different growth attributes. Over a 45-day period, PEG treatments (0.5% and 1.5%) proved more efficient compared to sucrose in suppressing in vitro growth, with reduced shoot lengths (0.92 and 0.57 cm), dry weight (0.04 and 0.02 g), and fresh weight (0.06 and 0.04 g). PEG also significantly enhanced phenolic levels (0.96 and 0.19 mg/g) and soluble sugars (4.07 and 4.12 mg/g) while reducing total protein level (2.38 and 2.32 mg/g) and total chlorophyll content (0.17 and 0.14 mg/g). The Pearson correlation analysis showed a negative association between phenolic levels and total chlorophyll content, chlorophyll a, and chlorophyll b. The length of the shoot had a negative relationship with phenolic level but a positive relationship with both fresh and dry weight. The principal component analysis revealed that total sugars and phenolics that were grouped separately from other variables led to stronger responses to osmotic stress. These outcomes suggested that higher PEG was successful in reducing in vitro growth throughout short-term preservation in comparison to sucrose. The outcomes of this research could be applied for the in vitro conservation of medical plants in the future.