پديد آورندگان :
مداحي نسب، محسن دانشگاه زابل - دانشكده كشاورزي - گروه زراعت، زابل، ايران , موسوي نيك، محسن دانشگاه زابل - دانشكده كشاورزي - گروه زراعت، زابل، ايران , قنبري، احمد دانشگاه زابل - دانشكده كشاورزي - گروه زراعت، زابل، ايران , سيروس مهر، عليرضا دانشگاه زابل - دانشكده كشاورزي - گروه زراعت، زابل، ايران , كوهستاني، شاپور دانشگاه جيرفت - دانشكده كشاورزي - گروه مهندسي آب، كرمان، ايران
كليدواژه :
زنجيره غذايي , زيست فراهمي , فاكتور انتقال , فلز سمي , كم آبي
چكيده فارسي :
هدف از اين تحقيق بررسي تأثير كم‌آبي بر قابليت انباشت زيستي و زيست‌فراهمي دو فلز سمي سرب و كروم براي گياه جو بود كه در يك آزمايش مزرعه‌اي دوساله، با اعمال سه سطح كم‌آبي با (آبياري در 100 (شاهد)، 75 و 50 درصد ظرفيت زراعي) انجام شد. نتايج نشان داد كه در همه موارد غلظت سرب و كروم در ريشه‌‌هاي گياه جو بيشتر از شاخساره بود و با افزايش تنش خشكي، افزايش غلظت سرب در ريشه‌ها معني‌دار نبود اما در شاخساره افزايش معني‌دار داشت درحالي‌كه غلظت كروم در هر دو بخش گياه كاهش معني‌دار داشت. با افزايش تنش خشكي، فاكتور انباشت شاخساره براي سرب افزايش و براي كروم كاهش يافت. همچنين با افزايش سطح كم‌آبي، فاكتور انباشت ريشه براي كروم كاهش يافت در حالي‌كه فاكتور انتقال براي هر دو عنصر افزايش يافت اما افزايش آن براي سرب برجسته‌تر بود. فاكتور انباشت شاخساره براي سرب با افزايش وزن خشك شاخساره بصورت خطي كاهش يافت (0٫86-=β) اما فاكتور انباشت شاخساره براي كروم افزايش يافت (0٫62 =β). مدل رگرسيوني وزن خشك ريشه، فاكتور انباشت ريشه براي كروم را با (0٫85=β ) پيش‌بيني كرد. مدل رگرسيوني وزن خشك كل گياه توانست فاكتور انتقال سرب را با (0٫89- =β) و فاكتور انتقال كروم را با (0٫67- =β) پيش‌بيني كند. در اين آزمايش ضرايب انباشت و انتقال زيستي مورد مطالعه همگي كمتر از يك بدست آمد، بنابراين گياه جو زراعي نسبت به سرب و كروم موجود در خاك، گياهي اجتناب كننده است و در شرايط كم‌آبي فزاينده در شرايط مزرعه، اين فلزات سمي را به زنجيره غذايي انتقال نمي‌دهد.
چكيده لاتين :
Introduction: The use of sewage sludge, which is mixed locally with poultry waste and is available at a
relatively low cost, improves the circulation of nutrients and organic matter in the soil, reduces the concentration
of CO2 in the atmosphere, and increases the level of soil organic carbon. Fertilization with this method is of
particular importance in soils of arid and semi-arid regions that face erosion and organic matter reduction.
However, there are concerns about the presence of essential and unnecessary heavy metals such as Cd, Cr, Cu,
Ni, Pb, and Zn that enter the environment from domestic, light industrial, commercial and municipal wastewater
sources and can lead to soil contamination and eventually enters the food chain through absorption, transport,
and accumulation in agricultural and non-agricultural products and has threatened human and animal health.
Phytoremediation is the cleaning up of polluted terrestrial areas and aquatic sites from heavy metal and organic
contaminants by green plants. An appropriate plant for phytoremediation should ideally have a high ability to
translocate contaminants into the plant shoot. However, the toxicity of the remains of these plants has become a
severe problem for human health. Iran is an arid and semi-arid country and many soils face the problem of using
animal manure sources with sewage sludge and the possibility of contamination with heavy metals. Farmers
cultivate the barley plant (Hordeum vulgare L.) in these areas widely, and it has a significant role in the food
chain of livestock and humans. Therefore, in this study, we evaluated the barley plant in terms of lead and
chromium accumulation by increasing drought levels in the field.
Materials and Methods: It was a two-year field experiment with three irrigation levels (irrigation per 100
(control), 75 and 50% of field capacity). The amount of chromium and lead in soil and plant samples was
measured using atomic spectroscopy with flame mode after extraction by digestion in acid. We used bioconcentration
coefficients including root bioaccumulation factor (
metal concentration of root
metal concentration of soil
), shoot
bioaccumulation factor (
metal concentration of aerial parts
metal concentration of soil
) and translocation factor (
metal concentration of aerial parts
metal concentration of root
) to
measure the plants bio-accumulation capacity. A plant with a root bioaccumulation factor bigger than one and a
bio-translocation factor of less than one is suitable for plant stabilization of elements. In contrast, a plant with a
shoot bioaccumulation factor and bio-translocation factor of more than one and root bioaccumulation factor of
less than one is suitable for plant extraction of elements from the soil.
Results and Discussion: After barley harvest, the average concentration of lead and chromium in soil
decreased by 23% and 17% compared to before harvest. The results of the analysis of variance showed that the
effect of experimental years was significant on the concentration of chromium in the soil and the aerial part of
barley and shoot bioaccumulation and root bioaccumulation factor of the same elements in the barley (p<0.05).
The effect of drought was significant on the shoot and root dry weight, chromium concentration in both shoots
and roots, lead concentration in shoots, lead and chromium shoot bioaccumulation factor, chromium root
bioaccumulation factor, and lead bio-translocation factor (p<0.01) and chromium bio-translocation factor
(p<0.05) but the interaction effect of year and drought was not significant on any of these traits. In all cases, the
concentration of elements in the roots was higher than the aerial part, and with increasing drought stress, the
concentration of lead in the roots remained constant but increased in the aerial parts while the concentration of
chromium decreased. As the amount of drought increased, the shoot bioaccumulation factor increased for the
lead but decreased for the chromium. The root bioaccumulation factor of chromium also decreased while the translocation factor increased for both elements, but the increase was more pronounced for the lead. Lead shoot
bioaccumulation factor decreased linearly with an increasing dry weight of aerial parts (β = -0.86), but chromium
shoot bioaccumulation factor increased (β = 0.62). Root dry weight predicted chromium root bioaccumulation
factor (β = 0.85). The total plant dry weight regression model could predict the lead translocation factor (β = -
0.89) and chromium transfer factor (β = -0.67).
Conclusion: In this experiment, the studied bioconcentration coefficients were all less than one. So, barley is
an avoidant plant when encountered with lead and chromium in the soil, and in increasing drought conditions in
the field, it does not translocate these toxic metals to the food chain.
