Adverse environmental conditions at planting, such as cold temperature or water limitation, can lead to a reduced level of seed germination and plant establishment for cotton. Cold atmospheric-pressure plasma (CAP) treatment of cotton seeds prior to planting may help alleviate this problem. CAP is ionised gas that has a range of biological activities due to the formation of a mix of reactive oxygen and nitrogen species (RONS), excited molecules, charged particles and UV photons. Our results show that a 27 minutes CAP treatment using air can significantly increase water absorption of the seed, and improve warm germination, metabolic chill test germination and chilling tolerance in cotton. We also observe that the beneficial effect of CAP treatment is long-lasting and stable as improved germination activity is still seen when treatment occurs 4 months before germination testing, suggesting that future large-scale industrial seed plasma treatments may still be effectively applied well (months) before the seed planting. We conclude that CAP treatment is a promising new tool for use in the cotton industry that has the potential to significantly improve plant establishment in a wider range of environmental conditions.

Climatic variability, typified by erratic heavy-rainfall events, causes waterlogging in intensively irrigated crops and is exacerbated under warm temperature regimes on soils with poor internal drainage. Irrigated cotton is often grown in precisely these conditions, exposing it to waterlogging-induced yield losses after substantial summer rainfall. This calls for a deeper understanding of mechanisms of waterlogging tolerance and its relevance to cotton. Hence this review suggests possible causes of waterlogging-induced yield loss in cotton and approaches to improvement of waterlogging tolerance, drawing upon the slight body of published data in cotton and principles from other species. The yield penalty depends on soil type, phenological stage and cumulative period of root exposure to air-filled porosities below 10 %. Events in the soil include O₂ deficiency in the root zone that changes the redox state of nutrients, making them unavailable (e.g. nitrogen) or potentially toxic for plants. Furthermore, root-derived hormones that are transported in the xylem have long been associated with oxygen deficits. These belowground effects (impaired root growth, nutrient uptake and transport, hormonal signalling) affect the shoots, interfering with canopy development, photosynthesis and radiation-use efficiency. Compared with the more waterlogging-tolerant cereals, cotton does not have identified adaptations to waterlogging in the root zone, forming no conspicuous root aerenchyma and having low fermentative activity. We speculate that these factors contribute substantially to the sensitivity of cotton to sustained periods of waterlogging. We discuss the impact of these belowground factors on shoot performance, photosynthesis and yield components. Management practices, i.e. soil aeration, scheduling irrigation and fertilizer application, can reduce waterlogging-induced damage. Limiting ethylene biosynthesis using anti-ethylene agents and down-regulating expression of genes controlling ethylene biosynthesis are strong candidates to minimize yield losses in waterlogged cotton crops. Other key pathways of anoxia tolerance are also cited as potential tools towards waterlogging-tolerant cotton genotypes.