The Effect of CO2 Enrichment on Leaf Anatomical Traits of Two Ficus Ornamental Species

 Since the beginning of the industrial revolution, the indiscriminate consumption of fossil fuels has led to a dramatic increase in the concentration of atmospheric carbon dioxide. Over the past few decades, the concentration of atmospheric carbon dioxide has increased from 280 to 370 ppm and is expected to increase by about 1.8 ppm each year. Carbon dioxide, such as light, appropriate temperature, water and nutrients, is one of the essential nutrients needed by plants, which is currently less than required by plants. In general, plants need to absorb water from the soil and carbon dioxide from the atmosphere and use it in photosynthesis, which This is done by absorbing carbon dioxide through the through the pores. In general, stomatal properties have a major influence on the response of plants to carbon dioxide treatment. Leaf  morphology, including stomatal density, may have a significant effect on the response of plants to carbon dioxide. There seems to be a great deal of variation among plant species in terms of how stomata density changes with increasing CO2 concentration. The opening and closing of the stomata through carbon dioxide absorption, regulates the amount of water wasted when adverse environmental conditions. In fact, increasing carbon dioxide in plants reduces stomatal conductance and transpiration, increases water use efficiency, photosynthesis rate and higher light utilization efficiency. 

 This study was conducted as a split plot experiment based on a completely randomized design with three replications in the research greenhouse of Ferdowsi University of Mashhad. Treatments included three concentrations of carbon dioxide (380 ppm as control, 700 and 1050 ppm) as the main plot and two species of ornamental ficus (Benjamin and Elastic) as sub plots. At first, cuttings were rooted in boxes containing washed sand infused with carbendazim for 8 weeks. After rooting, the cuttings were transferred to culture media containing appropriate soil mixture and exposed to different concentrations of carbon dioxide for 16 weeks. Were affected. Mean daily temperature of 25 and mean night temperature of 18 °C and 65% humidity were considered equal for all treatments. Then, after the treatments, Stomatal traits were measured.

 The results showed that high concentrations of carbon dioxide can affect the anatomical traits of Ficus ornamental species. In this study, the results obtained from the analysis of variance of the studied traits showed that the effect of different concentrations of carbon dioxide was not significant only for the stomatal index, but for other traits studied in this study. The main effect of carbon dioxide concentration was significant at 1% probability level.The results showed that the traits of stomata diameter in plant species and different concentrations of carbon dioxide were significant at 5 and 1% probability levels, respectively. Also with increasing the concentration of carbon dioxide the diameter of the stomatal decreased so that the highest stomatal diameter was related to the concentration of 380 ppm and the lowest to the concentration of 1050 ppm. In fact, increasing the concentration of carbon dioxide from the level of 380 to 1050 ppm led to a decrease of 19.91 percent in the diameter of the stomatal. Increasing the concentration of carbon dioxide in the environment of plants, initially increases the slope of the concentration of carbon dioxide between the surrounding air and the chamber under their stomata, and then more carbon dioxide through the pores leads to a decrease in the slope due to the abundance of carbon dioxide in the chamber below the stomata, This action reduces the diameter of the stomatal. As the concentration of carbon dioxide increased the stomatal cell density and stomatal area. Among the high concentrations of carbon dioxide the concentration of 700 ppm affected most of the traits, including stomatal diameter, stomatal area, epidermal cell density, stomach length and stomach width. though there was no significant difference between high concentrations of carbon dioxide (700 and 1050 ppm). According to the results of this study, it seems that anatomical traits are influenced by environmental factors and are not recognized as a hereditary factor. Among the species, the elastica species showed the most reaction to carbon dioxideal. 

 In general, clarifying the stomatal response to carbon dioxide concentration is important for understanding the stomatal physiology and gas exchange between vegetation and the In general, stomatal properties have a major influence on the response of plants to carbon dioxide treatment. Carbon dioxide at appropriate concentrations can increase growth and also affect the stomach properties to allow the plant to adapt to environmental conditions.