Combined effects of drought and CO₂ enrichment on foliar metabolites of potato (Solanum tuberosum L.) cultivars

Figures & data

Figure 1. Effects of CO₂ enrichment, genotype, and water stress on changes of potato LWP. Changes of leaf water potential (LWP) in two potato cultivars, Harley Blackwell (HB) and Snowden (SD), when plants were subjected to progressive drought at 0, 3, 6 and 9 days (d) after water was withheld at ambient (400 ppm) and elevated (800) CO₂ levels. Control: well-watered condition; Drought: water deficit condition. Error bars represent SEM (n = 6). The ANOVA for the treatments and duration of drought (days) are also given as *; P < 0.05; **; P < 0.01.

Figure 2. Diagram of foliar metabolic changes due to water stress and CO₂ enrichment in Harley Blackwell. The x-axis shows days of drought treatment. The y-axis shows leaf metabolite concentrations. The open and closed circle represents well-watered (C) and drought (D) condition. The grey and black color represents ambient (400 ppm) and elevated (800 ppm) CO₂ levels. Error bars represent SEM (n = 8). Abbreviations are for carbohydrates, CB (Suc, sucrose; Raff, raffinose; Mal, maltose; Pin, pinitol; Rib, ribose; Fru, fructose; Glc, glucose; myo-ino, myo-inositol; Stch, leaf starch), amino acids, AA (Gly, glycine; Ser, serine; Leu, leucine; Phe, phenylalanine; Val, valine; Ala, alanine; Asp, aspartate; Ile, isoleucine; Pro, proline; Phe, phenylalanine), and organic acids, OA (Mala, malate; Fum, fumarate; Succ, succinate; Cit, citrate; cis-acon, cis-aconitate; Oxo, 2-oxoglutaric acid; Quin, quinate; Malo, malonate; Male, maleate; Glyc, glycerate; Shik, Shikimate). Put, Putrescine

Figure 3. Diagram of foliar metabolic changes due to water stress and CO₂ enrichment in Snowden. Other details are as in Figure 2.

Table 1. Analysis of variance (ANOVA) results for leaf water potential and metabolites. Treatment effects of CO₂, drought (D), and cultivar (C) and their interactions on the leaf water potential and responses of leaf metabolites.

	CO2	C	D	CO2 × C CO2 × D		C × D
				Carbohydrates
Fructose	**	*	**	**	**	**	ns
Glucose	**	**	**	**	**	**	**
Sucrose	**	**	**	ns	**	**	*
Ribose	ns	ns	**	*	**	ns	ns
myo-inositol	**	**	**	ns	**	**	ns
Maltose	*	**	**	ns	**	**	**
Pinitol	ns	ns	**	ns	**	ns	*
Raffinose	**	**	**	**	**	**	**
Starch	ns	ns	**	ns	ns	ns	ns
				Organic acids
Fumarate	ns	ns	**	*	**	ns	ns
Citrate	ns	ns	**	ns	**	**	**
2-oxoglutarate	ns	*	**	*	**	ns	*
cis-aconitate	**	ns	**	*	**	**	ns
Glycerate	**	ns	**	ns	***	ns	**
Succinate	ns	ns	**	ns	ns	ns	ns
Maleate	**	ns	**	ns	**	**	**
Malate	ns	ns	**	ns	**	**	**
Malonate	**	**	**	ns	**	**	**
Shikimate	**	ns	**	ns	ns	ns	*
Quinate	**	**	**	ns	**	**	**
				Amino acids
Aspartic acid	*	ns	**	ns	**	ns	ns
Alanine	**	ns	**	ns	**	ns	ns
Glycine	ns	**	**	ns	**	**	**
Serine	**	ns	**	**	**	ns	ns
Isoleucine	ns	**	**	**	ns	**	**
Leucine	**	**	**	**	**	**	**
Valine	*	**	**	**	**	**	**
Phenylalanine	**	**	**	*	**	**	**
Proline	**	**	**	ns	**	**	ns
Putrescine	**	*	**	ns	**	**	**

Probabilities were determined using a two-way ANOVA procedure and denoted as *, P ≤ 0.05; **, P ≤ 0.01; and ns, P > 0.05 (not significant).

Figure 4. One-way Hierarchical clustering analysis of metabolites in two potato cultivars, Harley Blackwell (HB) and Snowden (SD) across drought and CO₂ treatments. Heatmap with hierarchical clustering analysis showing either the increase (shown in yellow) or decrease (shown in blue) of leaf metabolites in response to time of drought treatment (0, 3, 6, and 9 days), and CO₂ treatments (ambient, 400 ppm vs. elevated, 800 ppm) in the HB (A) and SD (B). Values are given as ratios obtained from drought and well-watered (control) treatments and are shown in gradations from 0.2–5× (see scale bar). Ratios that were unchanged are shown in black. AU represent approximately unbiased P-values (0–100%, the higher the number the more significant).