Biostimulant Capacity of an Enzymatic Extract From Rice Bran Against Ozone-Induced Damage in Capsicum annum

Abstract

Ozone is a destructive pollutant, damaging crops, and decreasing crop yield. Therefore, there is great interest in finding strategies to alleviate ozone-induced crop losses. In plants, ozone enters leaves through the stomata and is immediately degraded into reactive oxygen species (ROS), producing ROS stress in plants. ROS stress can be controlled by ROS-scavenging systems that include enzymatic or non-enzymatic mechanisms. Our research group has developed a product from rice bran, a by-product of rice milling which has bioactive molecules that act as an antioxidant compound. This product is a water-soluble rice bran enzymatic extract (RBEE) which preserves all the properties and improves the solubility of proteins and the antioxidant components of rice bran. In previous works, the beneficial properties of RBEE have been demonstrated in animals. However, to date, RBEE has not been used as a protective agent against oxidative damage in agricultural fields. The main goal of this study was to investigate the ability of RBEE to be used as a biostimulant by preventing oxidative damage in plants, after ozone exposure. To perform this investigation, pepper plants (Capsicum annuum) exposed to ozone were treated with RBEE. RBEE protected the ozone-induced damage, as revealed by net photosynthetic rate and the content of photosynthetic pigments. RBEE also decreased the induction of antioxidant enzyme activities in leaves (catalase, superoxide dismutase, and ascorbate peroxidase) due to ozone exposure. ROS generation is a common consequence of diverse cellular traumas that also activate the mitogen-activated protein kinase (MAPK) cascade. Thus, it is known that the ozone damages are triggered by the MAPK cascade. To examine the involvement of the MAPK cascade in the ozone damage CaMPK6-1, CaMPK6-2, and CaMKK5 genes were analyzed by qRT-PCR. The results showed the involvement of the MAPK pathway in both, not only in ozone damage but especially in its protection by RBEE. Taken together, these results support that RBEE protects plants against ozone exposure and its use as a new biostimulant could be proposed.

A new biostimulant derived from soybean by-products enhances plant tolerance to abiotic stress triggered by ozone

“…The selected plants and the treatment applied were carried out according to previous work by the group [ 15 ] . Capsicum annum L. var.…”

“…After eight days of transplantation, 20 pepper plants were selected and divided in 4 groups (5 plants for group): control plants (Ct), control plants under O 3 exposition (Ct + O 3 ), plants treated with OEE (OEE) and plants treated with OEE under O 3 exposition (OEE + O 3 ). Following protocol previously describe by us [ 15 ], to evaluate the protection capacity of the treatment with OEE, plants were foliar sprayed a total of 4 times at five-day intervals, with an aqueous solution of OEE at 0.1% (groups OEE and OEE + O 3 ) or distilled water (groups Ct and Ct + O 3 ). After 5 days of the last spray treatment, Ct + O 3 and OEE + O 3 plants were transferred to another phytoclimatic chamber with an ozone generator (ZONOSISTEM GM 5000 O 3 Generator) attached and exposed to 3 consecutive fumigations with 100 ppb of O 3 for 6 h (from 10:00 am to 4:00 pm).…”

“…Through the use of enzymatic technology, our group has already developed a rice bran extract with bio-stimulant properties that protected pepper plants against acute exposure to O 3 [ 15 ]. Thus, we have extended this technology to other agricultural by-products such as the soy pulp, also called okara.…”

“…The elevated level of bioactive compounds present in OEE and its potent antioxidant activity has prompted us to explore its potential as plant biostimulant. Similar to our previous work [ 15 ], we opted for pepper plants ( Capsicum annuum ) for this research due to the global significance of the pepper crop. Capsicum pepper is among the most widely cultivated vegetable crops internationally, experiencing a substantial increase in total production in recent years, reaching around 40 million tons in 2020 [ 19 ].…”

Wood Distillate Mitigates Ozone-Induced Visible and Photosynthetic Plant Damage: Evidence from Ozone-Sensitive Tobacco (Nicotiana tabacum L.) BelW3

“…To date, numerous molecules have been tested which could protect plants from the oxidative effects of O 3 [14][15][16][17][18][19][20][21]; however, some of them are synthetic, with their environmental toxicity still poorly understood [21]. In this context, natural or circular economy-based solutions would, therefore, be more ecologically sound.…”