Investigating the Effect of Environmental Stresses on the Growth and Development of Giant Reed (Arundo donax) under the Climatic Conditions of Mashhad City

Drought stress is one of the main environmental factors affecting the growth and productivity of plants around the world. Periods of severe drought are predicted to increase significantly in the near future, particularly as a result of extreme heat waves. Salinity is also one of the most important challenges facing the food supply for the world's population in the future, and the degree and time of exposure to stress can make this challenge stronger or weaker.Environmental limitations affecting plant growth, development and performance of physiological processes during plant response to stress provide important information about the plant mechanism, which is useful for eliminating or reducing the harmful effects of stress in plant tissues. The negative effects of climate change (such as drought, sea level rise, and global warming), as well as the salinization of agricultural land, and have been cited as one of the most important problems of the World Agriculture Organization (FAO).Understanding the relationship between changes in environmental conditions and climate change and Arundo donax with regard to the growth of coastal native species and also understanding the water wastage by this plant compared to coastal native plants is vital to remove this plant in the current situation where there is drought in most areas.In this situation, it is necessary to know how different environmental factors such as salinity levels, dryness, temperature, nutrients, light and fire affect the growth and invasion of Arundo donax for long-term and large-scale control. The purpose of this research is to obtain valuable information about the growth and development of existing ecotypes of the Arundo donax plant in Iran and the effect of various environmental factors on the germination, growth and fertility of this plant in order to plan for the long-term restoration of river ecosystems and how to control and The fight or its optimal use should be determined.

In order to investigate the effect of drought and salinity treatment on the growth and establishment of the rhizome of Arundo donax, an experiment was conducted in 2021 using rhizomes collected from the ecotype of Gorgan city and factorially in the form of a randomized complete block design in 3 replications in the research farm of Ferdowsi University of Mashhad. The experimental treatments included different levels of drought stress {100%, 75% and 50% of crop capacity} and different levels of salinity stress {0 (distilled water), 4, 8 and 12 dS/m}.

The general results of the experiment showed that the presence of salinity and drought stresses both decrease the growth and development indicators of this plant, and the presence of these two environmental stresses can increase the indicators of biomass of aerial organs, biomass of underground organs, plant height, and stem diameter. The effect of salinity stress on the reduction of the measured indices was less than that of drought stress, so that the difference between the levels of salinity stress at different levels of drought stress in all the measured indices, except the shoot biomass, had insignificant differences with each other, but in the comparison of the effect of drought stress at different levels of the surface together we come to the conclusion that drought stress alone leads to a significant decrease in growth indicators compared to the control treatment. The maximum amount of shoot biomass in non-stress conditions (control) was 2840 (gr), and with the increase of salinity and drought stress levels, this value decreases, so that the lowest amount of biomass in drought stress and maximum salinity conditions was 988 (gr). The biomass of the shoots of Arundo donax increased over time in different levels of salinity and drought stress, and its value was from less than 300 grams at the beginning of the growing season in all stress levels to more than 1000 to 2500 (gr) at the end of the growing season in different stress levels. 

The parameters obtained from the effect of salinity and drought stress on the stem diameter, plant height and leaf surface of Arundo donax showed that this plant showed some resistance under minor drought stress and these indicators decrease less in it, but in severe drought stress this amount decreased sharply. The results of analysis of variance of this experiment also showed that salinity and drought treatment and their interaction led to a significant difference with the control treatment. The simple effect of salinity treatment showed a significant difference in other indices compared to the control treatment, except for the index of leaf area and stem diameter, however, the simple effect of drought treatment showed significance in all the measured indices.