Evaluation of Silicon and Proline Application on the Oxidative Machinery in Drought-Stressed Sugar Beet

Abstract

Drought stress deleteriously affects growth, development and productivity in plants. So, we examined the silicon effect (2 mmol) and proline (10 mmol) individually or the combination (Si + proline) in alleviating the harmful effect of drought on total phenolic compounds, reactive oxygen species (ROS), chlorophyll concentration and antioxidant enzymes as well as yield parameters of drought-stressed sugar beet plants during 2018/2019 and 2019/2020 seasons. Our findings indicated that the root diameter and length (cm), root and shoot fresh weights (g plant−1) as well as root and sugar yield significantly decreased in sugar beet plants under drought. Relative water content (RWC), nitrogen (N), phosphorus (P) and potassium (K) contents and chlorophyll (Chl) concentration considerably reduced in stressed sugar beet plants that compared with control in both seasons. Nonetheless, lipid peroxidation (MDA), electrolyte leakage (EL), hydrogen peroxide (H2O2) and superoxide (O2●−) considerably elevated as signals of drought. Drought-stressed sugar beet plants showed an increase in proline accumulation, total phenolic compounds and up-regulation of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) activity to mitigate drought effects. Si and proline individually or the combination Si + proline considerably increased root and sugar yield, sucrose%, Chl concentration and RWC, MDA and EL were remarkably reduced. The treatments led to adjust proline and total phenolic compounds as well as CAT and SOD activity in stressed sugar beet plants. We concluded that application of Si + proline under drought stress led to improve the resistance of sugar beet by regulating of proline, antioxidant enzymes, phenolic compounds and improving RWC, Chl concentration and Nitrogen, Phosphorus and Potassium (NPK) contents as well as yield parameters.

Salt and Drought Stress Responses in Cultivated Beets (Beta vulgaris L.) and Wild Beet (Beta maritima L.)

“…In plants, exogenous proline improves root surface to handle water deficit and nutrient deficiency [99]. Consistently, recent reports ascertained that the exogenous application of proline can minimize drought-induced damages in sugar beet [9,11,54]. For instance, proline treatment brought about significant increase in root and sugar yield, the percentage of sucrose, chlorophyll content, and RWC but decreased ROS production, lipid peroxidation, and electrolyte leakage, protecting the plants against water stress [54].…”

Bacillus thuringiensis and Silicon Modulate Antioxidant Metabolism and Improve the Physiological Traits to Confer Salt Tolerance in Lettuce

“…Under the two salinity levels, the excessive accumulation of O 2 − and H 2 O 2 was recorded in lettuce plants; this accumulation of reactive compounds can cause oxidative stress to lipids, proteins, and nucleic acids [65]. Also, the increase of reactive oxygen species was recorded under drought stress in sugar beet plants [72]. Nonetheless, the harmful impact of salinity was overcome by Si application and B. thuringiensis, which reflect a significant reduction in O 2 − and H 2 O 2 levels.…”

The Role of Plant Growth-Promoting Bacteria in Alleviating the Adverse Effects of Drought on Plants

“…The full development of the shoot system and sufficient stomatal opening are important factors for optimum photosynthesis; consequently, net photosynthesis is decreased due to a reduction in leaf numbers and an increase in leaf senescence during drought [52,53]. Plants expand the roots and create a branched root system to increase water uptake and overcome drought conditions [54,55].…”

“…The full development of the shoot system and sufficient stomatal opening are important factors for optimum photosynthesis; consequently, net photosynthesis is decreased due to a reduction in leaf numbers and an increase in leaf senescence during drought [52,53]. Plants expand the roots and create a branched root system to increase water uptake and overcome drought conditions [54,55]. Under drought stress, the stomatal pores are closed, resulting in a decreased carbon dioxide (CO 2 ) uptake and causing a partial reduction in molecular oxygen, i.e., an increase in the production of ROS such as hydroxyl radicals (OH • ), O 2…”