ويژگي هاي فيزيولوژيكي، مورفولوژيكي و بيوشيميايي چهار رقم انجير خوراكي و دو رقم بر انجير در پاسخ به تنش خشكي

Physiological, Morphological and Biochemical Characteristics of F our Edible Fig and two Capri F ig C ultivars in R esponse to Drought Stress

اثر تنش خشكي روي برخي از ويژگي هاي مورفولوژيكي، فيزيولوژيكي و بيوشيميايي شش رقم انجير (سبز، سياه، سياه درشت، شاه انجير، برانجير ويل و برانجير پوزدمبالي) طي دو سال مورد ارزيابي قرار گرفت. پژوهش به صورت آزمايش فاكتوريل در قالب طرح كاملاً تصادفي با چهار تكرار و سه سطح تنش خشكي شامل ظرفيت زراعي به عنوان شاهد و 50 و 25 درصد ظرفيت زراعي به ترتيب به عنوان تنش متوسط و تنش شديد اجرا شد. محتوي رطوبت نسبي آّب برگ، نشت الكتروليت ها، ميزان كلروفيل، پرولين، پروتئين و كربوهيدرات ها، ارتفاع بوته، وزن تر و خشك ريشه و اندام هوايي و غلظت پتاسيم و سديم نيز اندازه گيري گرديدند. با افزايش تنش خشكي ارتفاع بوته، وزن تر و خشك ريشه و ساقه كاهش يافت و بيشترين آن در تنش شديد مشاهده شد كه با شاهد و تنش متوسط اختلاف معني دار داشت. بيشترين كاهش محتواي نسبي آب برگ مربوط به ارقام سبز و سياه درشت و بالاترين ميزان نشت الكتروليت ها مربوط به رقم سياه بود. كاهش كلروفيل در رقم سبز بيشتر از ساير ارقام بود و كمترين آن در رقم سياه درشت مشاهده شد. بيشترين تجمع پرولين وكربوهيدرات به ترتيب مربوط به رقم برويل و ارقام برانجير ويل و سياه بود. همچنين بيشترين كاهش پروتئين در رقم سياه و سياه درشت مشاهده شد. حداكثر افزايش در ميزان پتاسيم و سديم مربوط به رقم سياه درشت بود. بر اساس نتايج به دست آمده ارقام سياه و برانجير ويل با داشتن برخي ويژگي هاي فيزيولوژيكي و بيوشيميايي مشابه، از نظر تحمل به خشكي تقريبا معادل يكديگر ارزيابي شدند.

Plant responses to water deprivation are usually monitored through selected parameters which have been proven to be good indicators of drought in different studies. Some of the most important standards for evaluating plants under drought stress are measurements of physiological, morphological and biochemical parameters. These parameters have been found to generally reflect drought adaptation and could be used to select drought-tolerant species suitable to cultivate in dry and/or semi-dried lands. In this study, the effect of drought stress on some above-mentioned parameters in six fig cultivars including Sabz, Siah, Siahe Dorosht, Shah Anjir, Bare Veil and Bare poozdombali was investigated through a two-year experiment. Materials and methods The study was conducted in a factorial experiment based on a complete randomized design with four replications and three drought stress levels including field capacity as the control and 50 and 25% of field capacity as mild and severe stress, respectively. Results The highest amount of reduction in the above-mentioned parameters was observed under severe stress showing significant differences with the control and mild stress. The highest amount of relative water content associated with Sabz and Siah Dorosht cultivars and the greatest level of electrolyte leakage belonged to Siah cultivar. Chlorophyll reduction in Sabz was higher than the others and the least was observed in Siah Dorosht. The greatest proline accumulation was related to Bare Veil and the highest carbohydrate accumulation belonged to Bare Veil and Siah cultivars. The highest amount of protein reduction was also observed in Siah and Siah Dorosht without a significant difference. Maximum increase in the amount of potassium and sodium was observed in Siah Dorosht cultivar. Discussion Results indicated that, Siah and Bare Veil cultivars had approximately similar physiological and biochemical characteristics, so they evaluated as drought tolerant cultivars. It seems that fig plant employs a combination of mechanisms to overcome drought stress. Osmotic regulation is the active regulation of the osmotic pressure of the fig plant tissue’s fluid to maintain the homeostasis of the tissue’s water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution) to keep the fluids from becoming too diluted or too concentrated. In this study, the two above-mentioned drought-tolerant fig cultivars synthesized considerable amounts of proteins, carbohydrates and proline to regulate their tissues osmotic pressure resulting in better growth under drought stress.