برخي پاسخ‌هاي فيزيولوژيكي و بيوشيميايي ارقام گندم نان به تنش سرما در مرحله گياهچه اي

Some physiological and biochemical responses of wheat cultivar seedlings to cold stress

ﺷﻨﺎﺳﺎﯾﯽ ﺳﺎز و ﮐﺎرﻫﺎي ﺗﺤﻤﻞ ﺑﻪ ﺗﻨﺶ ﺳﺮﻣﺎ، ﻧﻘﺶ ﺑﺴﺰاﯾﯽ در ﭘﺎﯾﺪاري ﻋﻤﻠﮑﺮد ﮔﻨﺪم دارد. در اﯾﻦ ﭘﮋوﻫﺶ، ﭘﺎﺳﺦﻫﺎي ﻓﯿﺰﯾﻮﻟﻮژﯾﮑﯽ و ﺑﯿﻮﺷﯿﻤﯿﺎﯾﯽ از ﻗﺒﯿﻞ ﻣﯿﺰان ﻣﺎﻟﻮنديآﻟﺪﻫﯿﺪ )MDA(، ﺷﺎﺧﺺ ﭘﺎﯾﺪاري ﻏﺸﺎ ﺳﻠﻮل )MSI( و ﻓﻌﺎﻟﯿﺖ ﺑﺮﺧﯽ آﻧﺰﯾﻢﻫﺎي آﻧﺘﯽاﮐﺴﯿﺪان ﭘﻨﺞ رﻗﻢ ﮔﻨﺪم ﻧﺎن ﭘﺎﯾﯿﺰه و ﯾﮏ رﻗﻢ ﻣﺘﺤﻤﻞ ﺑﻪ ﺳﺮﻣﺎ ﺑﻬﺎره ﺗﺤﺖ ﺷﺮاﯾﻂ ﺷﺎﻫﺪ )23 درﺟﻪ ﺳﺎﻧﺘﯽ-ﮔﺮاد(، ﺳﺎزﮔﺎري )ﭼﻬﺎر درﺟﻪ ﺳﺎﻧﺘﯽﮔﺮاد( و ﺗﻨﺶ ﺳﺮﻣﺎ )5- درﺟﻪ ﺳﺎﻧﺘﯽﮔﺮاد( در ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﺷﺪه و ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﻧﺸﺪه ﻣﻄﺎﻟﻌﻪ ﺷﺪ. ﻧﺘﺎﯾﺞ ﺗﺠﺰﯾﻪ وارﯾﺎﻧﺲ ﻧﺸﺎن داد ﮐﻪ در ﺻﻔﺖ ﺷﺎﺧﺺ ﭘﺎﯾﺪاري ﻏﺸﺎ )MSI(، ﺗﻔﺎوت ﻣﻌﻨﯽداري ﺑﯿﻦ ارﻗﺎم و ﺳﻄﻮح دﻣﺎﯾﯽ و در ﺳﺎﯾﺮ ﺻﻔﺎت، ﺑﯿﻦ اﺛﺮات ﻣﺘﻘﺎﺑﻞ آنﻫﺎ وﺟﻮد داﺷﺖ. ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺶ ﻧﺸﺎن داد ﮐﻪ ﮐﺎﻫﺶ دﻣﺎ، ﺳﺒﺐ اﻓﺰاﯾﺶ ﻣﻘﺪار MDA و ﮐﺎﻫﺶ MSI در ارﻗﺎم ﺷﺪ. ﺗﺤﺖ ﺗﻨﺶ ﺳﺮﻣﺎ، ﻣﯿﺰان ﭘﺮوﺗﺌﯿﻦ ﮐﻞ و ﻫﻤﭽﻨﯿﻦ ﻓﻌﺎﻟﯿﺖ آﻧﺰﯾﻢﻫﺎي ﺳﻮﭘﺮ اﮐﺴﯿﺪ دﯾﺴﻤﻮﺗﺎز، ﮐﺎﺗﺎﻻز، آﺳﮑﻮرﺑﺎت ﭘﺮاﮐﺴﯿﺪاز و ﮔﺎﯾﺎﮐﻮل ﭘﺮاﮐﺴﯿﺪاز در ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﺷﺪه اﻓﺰاﯾﺶ ﯾﺎﻓﺖ، درﺣﺎﻟﯽﮐﻪ در ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﻧﺸﺪه، اﯾﻦ ﺷﺎﺧﺺﻫﺎ ﺑﻪﻃﻮر ﻣﻌﻨﯽداري ﻧﺴﺒﺖ ﺑﻪ ﺷﺎﻫﺪ ﮐﺎﻫﺶ ﯾﺎﻓﺖ. ﺗﺤﺖ ﺷﺮاﯾﻂ ﺗﻨﺶ، درﺻﺪ ﺗﻐﯿﯿﺮات ﮐﺎﻫﺶ( ﺷﺎﺧﺺ ﭘﺎﯾﺪاري ﻏﺸﺎ و MDA ارﻗﺎم ﻧﻮرﺳﺘﺎر و ﺑﺎران ﻧﺴﺒﺖ ﺑﻪ ﺳﺎﯾﺮ ارﻗﺎم ﮐﻤﺘﺮ ﺑﻮد. ﺑﻪﻧﻈﺮ ﻣﯽرﺳﺪ ﮐﻪ ﮐﺎﻫﺶ ﻣﯿﺰان ﻓﻌﺎﻟﯿﺖ آﻧﺰﯾﻢﻫﺎي آﻧﺘﯽ اﮐﺴﯿﺪان در ﺷﺮاﯾﻂ ﺗﻨﺶ در ﮔﯿﺎﻫﺎن ﺳﺎزﮔﺎر ﻧﺸﺪه، ﻣﻨﺠﺮ ﺑﻪ ﮐﺎﻫﺶ ﺗﻮاﻧﺎﯾﯽ ﮔﯿﺎه در ﺗﺤﻤﻞ ﺻﺪﻣﺎت ﻧﺎﺷﯽ از ﺗﻨﺶ ﺷﺪ. ﺑﻨﺎﺑﺮاﯾﻦ، ﮐﺎﻫﺶ ﺧﺴﺎرت ﺳﻠﻮﻟﯽ و اﻓﺰاﯾﺶ ﻇﺮﻓﯿﺖ ﺳﯿﺴﺘﻢﻫﺎي دﻓﺎع ﺳﻠﻮﻟﯽ ﻧﺎﺷﯽ از ﻓﺮآﯾﻨﺪ ﺳﺎزﮔﺎري را ﻣﯽﺗﻮان ﻋﺎﻣﻞ اﺻﻠﯽ ﺗﺤﻤﻞ ارﻗﺎم ﺗﺤﺖ ﺗﻨﺶ ﺳﺮﻣﺎ داﻧﺴﺖ.

Identifying mechanisms involved in cold tolerance can play an important role in maintaining yield. In this study, physiological and biochemical responses, including malondialdehyde (MDA), cell membrane stability index (MSI), and activities of antioxidant enzymes in five autumn bread wheat cultivars and one spring tolerant cultivar in four treatments: under normal conditions (23°C), acclimation (4°C) and cold stress (-5°C) were studied in acclimated and non-acclimated wheat plants. Analysis of variance showed significant differences between the effects of cultivars and environment temperatures on the membrane stability index, while in other indices, significant differences derived between interactive effects. Results showed that lower temperatures increased MDA, while decreased MSI in different cultivars. As plants exposed to cold stress, their total protein content as well as activities of superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase increased only in cold-acclimated plants, while decreased significantly in non-acclimated strands. Results also showed lower decrease of membrane stability index and MDA in Norstar and Baran cultivars under stress conditions. It seems that in non-acclimated plants under cold stress, decrease in activity of antioxidant enzymes has impaired plant's ability to withstand stress. Therefore, a decrease in cell damages as well as an increase in capacity of cell defense systems, coming down to acclimation process, can be regarded as important factors contributing to tolerance to cold stress.