Abstract
Salicylic acid (SA) can induce plants to actively enhance abiotic stress resistance. Spraying SA to prevent cold stress in flue-cured tobacco fields can provide theoretical support and practical guidance for the actual protection from cold stress in fields at high altitude in Yunnan. The experiment was performed in Jianchuan County Yunnan Province, China. Honghuadajinyuan, a flue-cured tobacco variety with cold resistance, was used as the research object. SA was tested at two concentrations (0.05 [SA-1] and 0.1 [SA-1] mol L–1) relative to an untreated control (Control) to compare the quality of fresh tobacco leaves, curing characteristics, enzyme activity of antioxidants, and quality of the first-cured tobacco leaves. The tissue structure thickness, SPAD, and plastid pigment content of fresh tobacco leaves were least in the control; there was no significant difference between SA-1 and SA-2. The change of moisture content during curing was SA-1 > SA-2 > Control, and the water loss rate was Control > SA-2 > SA-1, and both varied greatly at 38–48°C. In each curing stage, the carbon and nitrogen metabolites and polyphenols changed most rapidly at 38°C, and the sugar metabolites changed as follows: Control > SA-1 > SA-2. The activities of the antioxidant enzymes superoxide dismutase, peroxidase, and catalase in fresh tobacco leaves were SA-1 > SA-2 > Control. Malondialdehyde content and the inactivation rate of antioxidant enzymes during curing was Control > SA-2 > SA-1. The economic character and sensory smoking quality of flue-cured tobacco leaves were SA-1 > SA-2 > Control. In high-altitude tobacco planting areas prone to cold stress in the field, early warning weather forecast and field spraying 0.05 mol L–1 SA are beneficial to protect and improve the quality of fresh tobacco leaves, curing characteristics, antioxidant system enzyme activities, and the quality of flue-cured tobacco leaves.
Highlights
Cold stress occurs at low but above-zero temperatures, and the agricultural loss caused by cold injury in the world costs hundreds of billions of dollars each year
A suitable concentration of salicylic acid could increase the activity of antioxidant enzymes such as superoxide dismutase (SOD) and POD in leaves, maintain the stability of membrane system, reduce the loss of leaf tissue cells, alleviate the damage caused by cold damage to leaf tissue structure, and improve the cold resistance of flue-cured tobacco in the period of harvesting and curing (Janda et al, 1999; Kang and Saltveit, 2002; Khan et al, 2015)
This study showed that the quality of tobacco leaves with high concentration of salicylic acid was not as good as that with low concentration
Summary
Cold stress occurs at low but above-zero temperatures, and the agricultural loss caused by cold injury in the world costs hundreds of billions of dollars each year. Cold stress can inhibit photosynthesis and respiration (Wang et al, 2008; Yadav, 2010). Plants will show phenotypic symptoms such as loss of water, wilting of leaves, fading of green, yellowing, decrease in leaf area, and even tissue death (Hussain et al, 2018). Cold injury in maize (Zea mays) from emergence to maturity will lead to a decrease in seed germination rate, hinder the growth of functional leaves, inhibit photosynthesis, slow dry matter accumulation and filling rate, and reduce yield and quality (Prasad et al, 1994). Soybean (Glycine max) suffering from low temperature at flowering will have a rapid decrease in the number of pods and seeds per plant, affecting the formation of seed pods, resulting in a decrease in yield and quality (Yang et al, 2004)
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