Biochemical and physiological responses of Brassica napus plants to humic acid under water stress

Abstract

This study examines the effects of humic acid (HA, control, 3 and 6 mg/L) on some biochemical and physiological parameters of rapeseed (Brassica napus L.) plants under different water supply conditions (60, 100, and 140 mm evaporation from class A pan). Water stress decreased chlorophyll a (Chl a) and total chlorophyll (Chl T ) content in plants but proline content partly increased with increasing water stress severity. Plants treated by HA had more Chl a and Chl T content under both well and limited water conditions. Appli cation of HA improved the PSII and peroxidase activity of rapeseed plants under all irrigation treatments. Ascorbate peroxidase activity under severe water stress condition increased by 70 and 95%, compared with that under moderate and well watering conditions, respectively. Catalase activity was 51 and 69% less under well watering than that of moderate and severe water stress conditions, respectively. The highest activity of ascorbate peroxidase was recorded in plants treated by 6 mg/L HA. HA treated plants had 42, 8.5, and 15% more soluble protein content under well watering, moderate and severe water stress conditions, respectively, compared with control plants. Malondialdehyde increased with increasing the severity of water stress, in con trast, application of HA significantly reduced the amount of this trait under water stress conditions. It was shown that application of HA increased the activity of antioxidant enzymes, improved PSII activity and con sequently decreased lipid peroxidation in rapeseed plants.

Drought stress mitigation with humic acid in two Cucumis melo L. genotypes differ in their drought tolerance

“…Th e activity of SOD, CAT and GR enzymes was signifi cantly increased (in Şemame respectively: 78%, 19% and 40%, in Ananas respectively: 1%, 32% and 7%) compared to the control plants (Table 4). Similar results have been reported by Lotfi et al (2015), Hafez and Seleiman (2017) and Kaya et al (2018). In addition to that, HA treatment signifi cantly stimulated the activity of SOD, CAT and GR antioxidant enzymes in both genotypes subjected to drought stress.…”

“…In HA treatments, plants exposed to drought stress showed a decrease in MDA content compared to plants not treated with HA and this result was more remarkable in the tolerant genotype Şemame. MDA is considered an indicator of lipid peroxidation assessment and damage to membranes (Lotfi et al 2015). In the study, HA treatment limited the oxidation stress in melon genotypes under drought stress conditions.…”

“…Various mechanisms have been developed by drought-tolerant plants to adapt to the stress. Examples of these mechanisms are: increased water uptake by developing large and deep root systems, reduction of water loss by accumulation of osmolites, prevention of membrane disintegration and enzyme activation, and increase in K and Ca ions uptake (Mahajan and Tuteja 2005;Lotfi et al 2015;Kaya et al 2018).…”

Humic acid protects against oxidative damage induced by cadmium toxicity in wheat (Triticum aestivum) roots through water management and the antioxidant defence system

“…Therefore, HA supplementation promoted enzyme and non-enzyme activity and hence it successfully alleviated stress-induced H 2 O 2 and TBARS content. These results are compatible with studies by García et al (2014) and (Lotfi et al 2015) which exhibited lower H 2 O 2 content and TBARS in HA-treated plants grown under stress.…”

Influence of Nostoc entophytum and Tetracystis sp. on Winter Survival of Rapeseed

“…Countless biotic and abiotic factors play an important role in the successful overwintering of rapeseed [20,50,51]. The foliage is responsible for the successful overwintering of rape [50] while warmer, sunnier winter periods help the process, presumably due to the extending of photosynthetic activity [52].…”