محمود راینی سرجاز - Department of Irrigation, Faculty of Agricultural Engineering; Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

Proper detection of plant physiological processes could help us to figure out the role ofenvironmental factors on plant responses to biotic and abiotic stresses. Employment oftracer techniques, such as stable isotopes technique is a good tool to track the effects ofenvironmental stresses on crop productivity. The aim of this research is to evaluate theeffect of different photosynthetic pathways, water stress, and genetically modified plantson plant carbon isotopic composition (δ (13)C ), as an indicator of physiological processesand environmental factors. In this research, randomized plant materials of some trees andcrops, with different climate habitats and photosynthetic pathways, such as fruit, fruitjuice, tuber, syrup and leaves were collected from market and some leaf samples werecollected from experimental sites. Collected samples were first oven-dried and coarsesamples were converted to fine powders, using Wiley mill. Subsamples of 4 to 5 mg ofplant materials were combusted under vacuum, using Vycor tubes containing cupricoxide and silver wire. Combustion took placed at 520oC for 5 hrs to produce carbondioxide. Carbon isotope composition (δ 13C ) was measured relative to PDBV. Mean δ 13Cof C(4) (-13.32x 10(-3)) plants was almost two times more enriched in (13)C, compared to thatof C(3) plants (-29.39x 10(-3)). Significant differences were found between C(4) plants forδ 13C . The δ (13)C values between C(3) plants were also significantly different. Water-stressedplants were more enriched in (13)C relative to well-watered ones. It is concluded thatphotosynthetic pathway and environmental factors have crucial impact on δ (13)C of planttissues.

carbon isotope composition, WUE, water stress, photosynthetic pathway