Table 1.

Summary of the effects of elevated CO₂, drought, high temperature and salinity on physiological, morphological and molecular characteristics of potato and acclimation/adaptation strategies.

	Responses to change in the growth environment			Acclimation/ Adaptation strategies
	Morphological	Physiological	Molecular
High CO2	• Increased plant biomass	• Increased photosynthesis	• Down-regulation of key	• Stomatal closure
				• Resource remobilization particularly nitrogen in plant
	• Increased tuber yield	• Changed respiration rates	• photosynthetic enzyme activities particularly RuBisCO.
		• Changed photorespiration rates
				• Decreased RuBisCO activity
	• Increased LAI
		• Reduced stomatal conductance
	• Increased leaf DM content
		• Reduced transpiration rates
		• Increased water use efficiency
		• Accumulation of non-soluble carbohydrates.
		• Increased leaf nitrogen content
Drought	• Reduced plant growth	• Declined photosynthesis	• Up-regulation of drought-responsive gene expression	• Stomatal closure
		• Changed respiration rates		• Increased root to shoot ratio.
	• Reduced plant biomass
				• Increased ABA synthesis
			• Down-regulation of key photosynthetic gene expression
		• Reduced chlorophyll content		• Increased osmolyte content.
	• Reduced tuber yield	• Reduced internal CO2 concentrations	• Reduced activities of key photosynthetic enzymes.	• Increased synthesis of drought-related proteins,
	• Reduced stolon and tuber number	• Reduced transpiration rates
			• Increased activities of starch degrading enzymes	• Narrower leaf with hair.
		• Starch mobilization to reducing sugars
				• Increased anti-oxidant
	• Reduced LAI
		• Tuber develops sugar ends
				• Increased glycoalkaloids
	• Increased leaf DM content
		• Tuber develops malformations (hollow heart, cracking and secondary growth)
	• Shorter plant height
	• Increased root to shoot ratio
		• Tuber develops internal brown spot
	• Delayed tuberization
	• Early senescence
High temperature	• Reduced plant growth	• Declined photosynthesis	• Increased activities of starch degrading enzymes	Increased synthesis of heat-shock proteins
	• Reduced tuber yield	• Reduced photosystem II activity
				• Increased transpiration
	• Increased leaf DM content	• Reduced sucrose translocation to tubers.
	• Decreased tuber DM content	• Starch mobilization to reducing sugars
		• Tuber develops sugar ends
	• Delayed tuberization
		• Tuber develops malformations (hollow heart, cracking and secondary growth)
		• Tuber develops necrosis
		• Tuber develops field sprouting
Salinity	• Reduced plant emergence	• Declined photosynthesis	• Increased activity of transmembrane transport proteins involved in Na+ transport to vacuole	• Stomatal closure
		• Reduced transpiration rates		• Increased ABA
	• Reduced root length and volume			• Increased proline
				• Increased Na+ transport across the tonoplast in exchange for H+
		• Reduced leaf water content
	Early haulm senescence
			• Reduced activities of nitrate reductase
				• Increased activity of antioxidant enzymes; ascorbate peroxidise, catalase, glutathione reductase and hydrogen peroxide
		• Reduced leaf osmotic potential
			• Down-regulation of genes coding for Photosystem I, Photosystem II and chlorophyll synthesis proteins
	• Reduced shoot biomass	• Increased total soluble solids
		Increased lipid peroxidation
	• Reduced tuber growth
				• Change in chloroplast ultra-structure
		• Increased leaf carbohydrate content
	• Decreased tuber DM content
		• Reduced tuber nitrogen content	• Change in gene expression related to carbohydrate and amino acid metabolism
	• Reduced tuber number
	• Reduced tuber yield

LAI, Leaf area index; DM, dry matter. Data were obtained from: High CO₂ (Sage et al., 1989; Mackowiak and Wheeler, 1996; Sicher and Bunce, 2001; Donnelly et al., 2001; Vandermeiren et al., 2002; Magliulo et al., 2003; Katny et al., 2005; Kaminski et al., 2014); Drought (Dalla Costa et al., 1997; Chen and Murata, 2008; Evers et al., 2010; Watanabe et al., 2011; Albiski et al., 2012; Wang-Pruski and Schofield, 2012; Obidiegwu et al., 2015; Zarzynska et al., 2017); High temperature (Burton, 1981; Hijmans, 2003; Timlin et al., 2006; Levy and Veilleux, 2007; Minhas, 2012; Bita and Gerats, 2013; Hancock et al., 2014; Rykaczewska, 2015; Tang et al., 2016; Trapero-Mozos et al., 2018); Salinity (Levy et al., 1988; Levy, 1992; Ghosh et al., 2001; Fidalgo et al., 2004; Aghaei et al., 2009; Legay et al., 2009;Queirós et al., 2009a,b, 2011; Akhtar et al., 2015; Jaarsma and de Boer, 2018).