Simultaneously evaluation of physiological and biochemical responses in the leaves and roots of Iranian common bermudagrass [Cynodon dactylon L. (Pers.)] accessions under a wide range of temperature fluctuations

Abstract

The average temperature of the earth's surface is increasing rapidly, negatively affecting the urban space's green cover. In this study, to identify Iranian common bermudagrass accessions which could endure a wide range of temperature fluctuations, and be identified as cold-heat tolerant accessions, seven cold-tolerant Iranian accessions including Taft, Naein, Malayer, Gardane-Heyran, Aligoudarz, Safashahr, and Gorgan along with Ahvaz accession as a native accession to tropical regions of Iran were subjected to five high-temperature regimes, including 35/30°C (control), 40/35°C (moderate heat stress), 45/40°C (severe heat stress), 50/45°C (extreme heat stress), and 50/50°C (high-extreme heat stress) day/night cycles for 21 days. At the end of this experiment, it was found that Gorgan and Safashahr accessions were able to endure the 50/45°C TR with acceptable turfgrass quality (heat-tolerant accessions). Ahvaz and Aligudarz accessions could withstand extreme heat stress, but their visual quality was weaker than the former group (semi-heat-tolerant). In contrast, Taft, Naein, Malayer and Gardane-Heyran accessions could not tolerate this harsh condition and their shoots were destroyed (sensitive accessions). Evaluation of physiological parameters (Tchl, RWC, EC and RV), osmolytes (proline, TSC and starch) and antioxidants (SOD, APX, CAT and POX) in leaves and roots after moderate heat stress showed that all parameters except RWC and root viability increased in all accessions. With rising temperature in the 45/40°C TR, root viability in sensitive, semi-tolerant and tolerant accessions increased by 170%, 99% and 143% respectively, and its rate in sensitive accessions was almost twice that of tolerant accessions, while there was no significant difference in the amount of stored starch in their roots. In the continuation of the experiment, when the heat stress became extreme, root viability in sensitive accessions was greatly reduced (89%) and its rate was almost 1/4 of that in tolerant accessions. In such a situation, sensitive accessions could only use 4% of their roots' starch reserves, while semi-tolerant and tolerant accessions used 35% and 47%, respectively. These findings provided that heat-tolerant plants with controlling respiratory rate in roots and efficiently breaking down starch storage to carbohydrates could provide the energy required for whole plant metabolic activities. This experiment also highlights the importance of simultaneously investigating evaluated parameters in leaves and roots.