بررسی تاثیر خشکی بر رشد، خواص کیفی و عناصر در گیاه ریحان آفریقایی (ocimum gratissimum)

انتخاب گونه های مقاوم و متناسب با اقلیم هر منطقه یکی از راه کارهای کارآمد تحت تنش به حساب می آید. بدین منظور این پژوهش با هدف بررسی پاسخ گونهo. gratissimum  به تنش خشکی در بهار و تابستان 1401 در گلخانه تحقیقاتی دانشکده کشاورزی دانشگاه فردوسی مشهد انجام شد. در ابتدا پیش تست اولیه بر روی گونه رایج o. basilicum و o. gratissimum انجام و نتایج نشان داد که وزن بوته و شاخص سبزینگی در گونه o. gratissimum نسبت به o. basilicum بطور معنی داری بالاتر است. در مرحله دوم تاثیر تنش خشکی بر گونه o. gratissimum  بررسی شد. در ابتدا نشاها تهیه و سپس به گلدان منتقل شدند و پس از استقرار کامل تنش خشکی (100 درصد ظرفیت زراعی و 50 درصد ظرفیت زراعی) اعمال و گیاهان تا مرحله گلدهی نگهداری شدند. سپس صفات وزن تر و خشک گیاه، ارتفاع، سطح برگ، حجم ریشه، شاخص سبزینگی، نشت غشا، فعالیت آنتی اکسیدانی، محتوی فنل و فلاونوئید، ویتامین ث، فعالیت آنزیم پراکسیداز، پرولین و غلظت عناصر غذایی (نیتروژن، فسفر، پتاسیم، آهن، روی، منگنز) اندازه گیری شد. نتایج حاصل از این پژوهش نشان داد وزن تر، وزن خشک، ارتفاع، سطح برگ، و قطر ساقه به ترتیب 61، 55، 51، 52، و 35 درصد در گیاهان تحت تنش نسبت به شاهد کاهش یافتند. گیاهان در شرایط تنش میزان شاخص سبزینگی بالاتر اما میزان فنل و فلاونوئید پایینتری را ثبت کردند. علاوه بر این محتوای عناصر نیتروژن، منگنز، روی، فسفر و پتاسیم تحت تنش به ترتیب 15، 31، 31، 21 و 22 درصد نسبت به گیاهان شاهد کاهش یافت. به نظر می رسد جذب عناصر غذایی بیش از شاخص های دیگر مانند متابولیت ها تحت تاثیر تنش قرار گرفته است که این مسئله نیاز به بررسی بیشتری دارد.

influence of drought stress on the growth of african basil (ocimum gratissimum).

1. introduction: increasing drought due to global climate change will reduce plant growth and thus reduce food production in natural ecosystems and agricultural systems. in response, plants undergo several physiological and morphological modifications like reduced transpiration and photosynthesis rate, osmotic adjustments, suppressed root and shoot growth, overproduction of reactive oxygen species (ros), modified stress signalling pathways, and senescence. to cope with these challenges, plant scientists will need to begin producing novel crop varieties that have increased yield, that are tolerant to abiotic stresses, and that have improved water and nutrient uptake efficiencies. among the methods available, knowing about the response of different plant species to drought stress and selecting resistant species is considered one of the efficient solutions. basil is one of the most popular and valuable vegetables, widely used around the world. it is marketed both in fresh and dried form for use in the spice and food industries and also as a medicinal plant with applications in the perfume, cosmetic, and pharmaceutical industries. this plant grows under warm conditions, but it is so sensitive to drought stress. the significant reduction under drought stress is widely reported.2. materials and methods: first, a pre-test comparing two species, ocimum basilicum and o. gratissimum, the results showed that the plant weight and chlorophyll in o. gratissimum species are significantly higher than basilicum. then, the main study was conducted to investigate the response of o. gratissimum species to drought stress in the climatic conditions of mashhad. in this research, seedlings of this species were prepared in the greenhouse and then transferred to pots, and after the complete establishment of water stress was applied, and the plants were kept until the flowering stage. the drought-stressed plants received half the amount of water compared to the control plants. all cultivation practices were carried out uniformly for all pots, and no fertilizers or additional substances were applied to the plants during the experiment. then the morphological characteristics (wet and dry weight of the plant, height, leaf area, and root volume), chlorophyll, relative water content, antioxidant activity, phenol and flavonoid content, vitamin c content, and concentration of nutrients (nitrogen, phosphorus, potassium, iron, zinc, manganese) were measured.3. results and discussion: the results of this research showed that fresh weight, dry weight, height, leaf area, root volume, and stem diameter decreased by 61, 55, 51, 52, 11, and 35% respectively, in stressed plants compared to the control. the indicators related to chlorophyll fluorescence were affected by drought stress in this plant, and except for fm and fv/fm, where ft and f0 increased by 20% and 24%, respectively, compared to the control plants. photosynthesis in these plants showed a significant decrease of 31% under the influence of the decrease in irrigation water, which was completely predictable. drought stress in this type of basil could not show significant effects on antioxidant capacity and vitamin c, while the amount of total phenol, total flavonoid, and chlorophyll showed a significant difference from control plants. chlorophyll increased by 5% in stressed plants, but total phenol and total flavonoid showed a significant decrease of 7% and 6%, respectively, compared to the control plants. in this experiment, the amount of proline was affected by drought stress and increased by 55%. the activity of the peroxidase enzyme also showed an increase of 68% in this plant under the stress of low irrigation. membrane leakage was also recorded at higher numbers in this plant under stress, increasing by up to 44%. according to the findings of this research, the concentration of macro and micro elements, except for iron, was affected by stress. thus, the content of nitrogen, manganese, zinc, phosphorus, and potassium in the plants that received less water decreased by 15, 31, 31, 21, and 22% respectively, compared to the control plants. it seems that in o. gratissimum, drought stress significantly decreases photosynthesis and macro and microelements, and finally biomass.4. conclusions: it seems that in normal conditions, o. gratissimum performs better than o. basilicum. under drought stress quality and biomass of o. gratissimum are significantly affected, and the absorption of nutrients is more impacted than other indicators, such as metabolites, but more research is needed with the presence of other species in different weather conditions and different degrees of stress.