Physiological performance and herbage yield of coriander affected by carbon quantum dots and titanium dioxide nanoparticles (Coriandrum sativum) under water deficit stress

Under water deficit stress condition, using nanoparticles could increase the growth and yield of medicinal plants. Under water deficit stress, the effects of carbon quantum dots (CQDs) and TiO ₂ nanoparticles (TiO ₂ -NPs) were investigated on physiological parameters and yield of coriander ( Coriandrum sativum L.). The experiment was arranged as factorial with randomized complete block design and three replicates in greenhouse. The first factor was different water deficit stress levels as control (no water deficit stress,100% FC), mild (50% FC) and high (25% FC) water deficit stress. The second factor was spraying nanoparticles at four levels consisted of control (distilled water), CQDs (10 mg L ^− 1 ), TiO ₂ -NPs (50 mg L ^− 1 ), and CQDs (10 mg L ^− 1 ) + TiO ₂ -NPs (50 mg L ^− 1 ). The relative water content (RWC), chlorophyll a (Chl a) and b (Chl b), plant height, dry herbage yield, EO content and yield of coriander decreased under water deficit stress, while, increases in malondialdehyde (MDA) and leaf proline (LP) contents, catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO) activities were observed. Under high water deficit stress, using CQDs + TiO ₂ -NPs increased the RWC (21%), Chl a (96%), Chl b (46%) and LP (45%) contents, CAT (53%), POD (11%) and PPO (16%) activities, dry herbage yield (49%), EO content (38%) and yield (105%) of coriander compared with control, while the MDA content decreased by 83%. Generally, we can conclude that CQDs + TiO ₂ -NPs improved the physiological performance, antioxidant enzymes activity, and dry herbage and EO yield of coriander under water deficit stress. This nanoparticle treatment could be recommended in cropping systems of coriander with water limitation.