Effect of Animal Manure and Biochar on Some Morphophysiological and Biochemical Characteristics of Pelargonium graveolens L. Under Water Deficit Stress

Document Type : Full Paper

Authors

• Reza Pourveiseh ¹
• Abdolhossein Rezaei Nejad ¹
• Sadegh Mousavi-Fard ²

¹ Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Lorestan, Iran

² Department of Horticultural Sciences, Faculty of Agriculture, Shahrekord University, Shahrekord , Chaharmahal and Bakhtiari, Iran.

Abstract

Keywords

• Drought
• Organic modifier
• Photosynthetic pigments
• Proline

Main Subjects

• Ornamental plant science

Extended Abstract

Introduction

The sweet-scented geranium (Pelargonium graveolens L.) is a medicinal-ornamental plant belonging to the Geraniaceae. It has many uses in the perfumery and pharmaceutical industries due to the presence of essential oils. Water is one of the most important environmental factors in the production of ornamental and medicinal plants, both from an ecological and physiological point of view, because it is involved in most of the internal processes of the plant and affects most of the metabolic activities of plant cells. The change of morphological, physiological and biochemical traits is one of the most important adaptation mechanisms of plants to drought stress conditions. Currently, it is a common method to use different types of animal manures in the soil to increase soil fertility. On the other hand, biochar increases soil fertility and resistance to environmental stresses due to its high ability to absorb and store nutrients and prevent their leaching. Even today, due to the decrease in the level of water resources and the problem of drought stress, one of the most important measures in agriculture is the production of drought-resistant ornamental plants and identifying the most important combination of planting substrates to increase drought resistance in different plants. Therefore, in this research, the effect of organic fertilizers on some morphophysiological and biochemical characteristics of the sweet-scented geranium, a medicinal plant, under water deficit stress conditions was investigated.

Materials and Methods

The current research was conducted in a factorial experiment, in a completely randomized design with two factors and four replications in 2022 in the research greenhouse of the Faculty of Agriculture of Lorestan University. The first factor included water stress at three levels of 20, 50 and 80% available water in the soil, and the second factor was six levels of planting substrate: control (a mixture of sand and agricultural soil in a ratio of 1:1), animal manure substrate (soil, sand, animal manure 25% by volume), biochar 5 g kg^-1 of control bed, biochar 10 g kg^-1 of control substrate, biochar 5 g kg^-1 of manure substrate, and biochar 10 g kg^-1 of manure substrate. For the preparation of biochar, the animal manure was packed in aluminum sheets and placed inside the electric furnace for 4 hours at a temperature of 500 Ċ so that the pyrolysis process took place. Pelargonium graveolens cuttings were prepared from the main branch of mother plants from the greenhouse of the Faculty of Agriculture and after rooting, they were planted in pots containing the desired substrate. After the establishment of the cuttings, the treatments of water deficit stress were applied, based on the calculating available water in the soil with the help of pressure plates and weight methods. Three months after the application of water deficit stress, the morphophysiological and phytochemical characteristics were measured.

Results and Discussion

The results showed that water deficit stress caused a decrease in the number of leaves, fresh and dry weight of aerial parts, dry weight of roots, photosynthetic pigments and essential oil yield, while root length and content of malondialdehyde, proline, ion leakage and essential oil percentage increased. The use of manure and biochar planting beds in stress conditions improved the growth characteristics and reduced the effects of water deficit stress, on the other hand, it decreased proline, electrolyte leakage, and malondialdehyde content. So, the lowest level of catalase enzyme activity, proline level, electrolyte leakage and malondialdehyde was obtained with the application of animal manure + 5 g kg^-1 of biochar, but it increased the percentage and yield of the essential oil. Drought stress reduces plant growth through stomatal and non-stomatal limitations and production of reactive oxygen species (ROS). The application of animal manure and biochar reduces the negative effects of drought stress and increases plant growth by increasing soil porosity, absorbing nutrients, stimulating growth hormones and maintaining soil moisture.

Conclusions

The results showed that water deficit stress condition caused an increase in electrolyte leakage, malondialdehyde concentration and essential oil percentage and a decrease in photosynthetic pigments, growth components (number of lateral branches and leaves, fresh and dry weight of shoots and roots) and essential oil yield of sweet-scented geranium plant. The use of planting beds containing animal manure and biochar in water deficit conditions caused a decrease in electrolyte leakage and malondialdehyde content, as well as an increase in the concentration of photosynthetic pigments and improved the growth characteristics of sweet-scented geranium. Also, the percentage and yield of essential oil increased. Hence this study suggests that better growth can be gained by application of animal manure and 5 g kg¹ biochar as a suitable substrate in Geranium graveolens pot cultivation.