Mesophyll conductance to CO2 and leaf morphological characteristics under drought stress during Quercus ilex L. resprouting

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Table II

Midday values of net photosynthesis (A), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), instantaneous water use efficiency (WUE_i = A / g_s), relative water content (RWC), PSII efficiency (ΦPSII), non-photochemical quenching of fluorescence (NPQ) and potential quantum yield of PSII at midday (F_v / F_m). Data are presented according to treatment (control, C; winter resprouts, RW; summer resprouts, RS), leaf orientation (north, south) and season (winter, summer). Values are mean ±SE of nine replicates. Significant differences across rows or columns (p ≤ 0.05) are indicated by different letters (treatment (a, b, c), season (A, B) and leaf orientation (α,β)).

			Treatments
	Season	Leaf orientation
			C	RW	RS
A (μmolm⁻² s⁻¹)	Winter	North	4.47 ± 0.32^aAα	4.84 ± 0.38^aAα	—
		South	5.67 ± 0.66^aAβ	6.82 ± 0.77^aAβ	—
	Summer	North	1.20 ± 0.20^aBα	3.28 ± 0.39^bBα	4.03 ± 0.81^bα
		South	0.87 ± 0.09^aBβ	4.55 ± 0.69^bBβ	5.35 ± 0.33^bβ

g_s (mmol m⁻² s⁻¹)	Winter	North	272.1 ± 34.3^aAα	300.6 ± 27.6^aAα	—
		South	253.1 ± 46.6^aAα	263.7 ± 40.0^aAα	—
	Summer	North	41.8 ± 2.9^aBα	123.9 ± 12.1^bBα	144.0 ± 12.2^bα
		South	37.6 ± 5.8^aBα	144.7 ± 21.9^bBα	165.3 ± 22.1^bα

C_i (μmol mol⁻¹)	Winter	North	291 ± 10^Aaα	278 ± 6^aAα	—
		South	241 ± 13^aAβ	240 ± 11^aAβ	—
	Summer	North	276 ± 8^aAα	248 ± 13^aBα	247 ± 8^aα
		South	283 ± 4^aBα	254 ± 12^bAα	240 ± 4^bα

WUE_i (μmol mmol⁻¹)	Winter	North	19.78 ± 3.4^aAα	17.95 ± 2.0^aAα	—
		South	26.13 ± 4.7^aAβ	29.44 ± 4.0^aAβ	—
	Summer	North	28.58 ± 3.8^aBα	26.82 ± 2.1^aBα	28.35 ± 5.1^aα
		South	24.14 ± 2.6^aAβ	32.63 ± 5.6^bAβ	33.95 ± 3.1^bβ

RWC (%)	Winter	North	75.5 ± 2.8^aAα	85.3 ± 1.4^bAα	—
		South	73.7 ± 1.5^aAα	83.0 ± 1.7^bAα	—
	Summer	North	67.8 ± 2.2^aBα	78.6 ± 2.1^bAα	77.6 ± 1.9^bα
		South	65.2 ± 1.2^aBα	77.9 ± 1.1^bAα	77.7 ± 1.4^bα

Φ _PSII	Winter	North	0.71 ± 0.01^aBβ	0.64 ± 0.03^aBα	—
		South	0.52 ± 0.07^aBα	0.56 ± 0.04^aBα	—
	Summer	North	0.09 ± 0.02^aAα	0.09 ± 0.01^aAα	0.08 ± 0.03^aα
		South	0.04 ± 0.02^aAα	0.086 ± 0.01^bAα	0.08 ± 0.01^bα

NPQ	Winter	North	0.17 ± 0.05^aAα	0.26 ± 0.09^aAα	—
		South	0.83 ± 0.25^aAβ	0.60 ± 0.13^aAβ	—
	Summer	North	2.36 ± 0.29^aBα	1.88 ± 0.20^aBα	1.93 ± 0.04^aα
		South	2.72 ± 0.22^bBα	2.01 ± 0.18^aBα	2.32 ± 0.26^aα

F_v / F_m	Winter	North	0.77 ± 0.01^aBα	0.75 ± 0.02^aBα	—
		South	0.76 ± 0.01^aBα	0.75 ± 0.01^aBα	—
	Summer	North	0.68 ± 0.03^aAα	0.68 ± 0.01^aAα	0.70 ± 0.02^aα
		South	0.65 ± 0.01^aAα	0.67 ± 0.03^aAα	0.66 ± 0.03^aα