Seasonal change in response of stomatal conductance to vapor pressure deficit and three phytohormones in three tree species

Figures & data

Figure 1. Climate diagram for Jinan, Shandong, China.

Table 1. Features of the experimental plants and leaf chamber temperature (T_b) during measurements.

Plant species	Month	Tb(°C)	Chest diameter of trees (mm)	Height of trees (m)
F. chinensis	June	30	150-200	7-8
	August	30
	October	20
P. alba var.	June	31	Seedling	0.5–1.3
	August	31
	October	25
P. tomentosa	June	32	Seedling	0.5–1.5
	August	31
	October	26

Table 2. Detection limits and recoveries of standards of GA₃, IAA, and ABA.

Phytohormones	Quantitative detection limit (ng/L)	Recovery (100%)
GA3	8.43	95.2 ± 7.9
IAA	3.77 × 10^−2	96.3 ± 8.2
ABA	12.5	95.9 ± 3.9

Table 3. The concentration of phytohormone (GA₃, IAA, ABA) and the ratios of GA₃/ABA and IAA/ABA in three tree species in Jinan.

Plant species	Month	GA3 (ng/(g FW))	IAA (ng/(g FW))	ABA (μg/(g FW))	GA3/ABA (10^−3)	IAA/ABA (10^−3)
F. chinensis	June	311.15 ± 14.75^a	10.74 ± 0.85^a	5.50 ± 1.05^a	56.57	1.84
	August	60.50 ± 2.07^b,c	1.94 ± 0.29^b,c	13.63 ± 0.94^b	4.44	0.14
	October	12.80 ± 0.49^b	2.85 ± 0.32^c	3.21 ± 0.72^c	3.99	0.89
P. alba var.	June	934.18 ± 31.75^d	5.21 ± 0.41^d	4.13 ± 1.28^a,c	226.19	1.26
	August	230.31 ± 18.65^a,c	1.79 ± 0.37^b,c	18.20 ± 1.74^d	12.66	0.10
	October	842.50 ± 28.50^d	1.37 ± 1.06^b	14.06 ± 1.76^b	59.92	0.10
P. tomentosa	June	324.22 ± 7.55^a	4.15 ± 1.05^d	13.47 ± 0.60^b	24.07	0.31
	August	315.33 ± 8.07^a	4.87 ± 0.27^d	16.24 ± 0.83^d	19.41	0.30
	October	414.71 ± 10.48^a	2.25 ± 0.33^b,c	22.99 ± 1.64^e	18.04	0.10

Note: The same letter in the same column represents no significant difference (Duncan test, P < 0.05, n = 3–5).

Figure 2. The responses of stomatal conductance (g_s), net photosynthesis rate (A_n), transpiration rate (E) and water use efficiency (WUE) to vapor pressure deficit (VPD) in F. chinensis, P. alba var. and P. tomentosa in Jinan, China. Error bars represent standard errors of g_s, A_n and E with 3–7 replicates measurements.

Figure 3. Comparison of stomatal conductance predicted by the Leuning model and measured data for the three tree species in Jinan, China. The diagonal line is the 1:1 relationship between predicted data and measured data. The σ value is the difference between the 1:1 line and measured data (Root Mean Square Error, RMSE).

Figure 4. Comparison of stomatal conductance predicted by the optimal stomatal model and measured data for the three tree species in Jinan, China. The diagonal line is the 1:1 relationship between predicted data and measured data. The σ value is the difference between the 1:1 line and measured data (Root Mean Square Error, RMSE).

Table 4. Nonlinear simulation formula of g_s to VPD and g_s-max corresponding to VPD and RH.

Plant species	Month	Nonlinear simulation formula (gs = a·exp(−0.5(ln(D/c)/b)^2), D = VPD)	Correlation coefficient (R^2)	VPD (kPa, gs = gs-max)	RH (%, gs = gs-max)	Mean monthly VPD in 2010 (kPa)	Mean monthly temperature in 2010 (°C)
F. chinensis	June	gs = 0.17exp(−0.5(ln(D/1.91)/0.75)^2)	0.962	1.91	60.14	1.43	25.8
	August	gs = 0.36exp(−0.5(ln(D/1.77)/0.63)^2)	0.845	1.77	57.88	0.61	25.1
	October	gs = 0.17exp(−0.5(ln(D/1.96)/0.76)^2)	0.994	1.96	12.31	0.78	15.3
P. alba var.	June	gs = 0.24exp(−0.5(ln(D/1.34)/0.89)^2)	0.979	1.34	69.98	1.43	25.8
	August	gs = 0.28exp(−0.5(ln(D/1.68)/0.83)^2)	0.995	1.68	64.18	0.61	25.1
	October	gs = 0.4exp(−0.5(ln(D/1.46)/0.75)^2)	0.973	1.46	49.21	0.78	15.3
P. tomentosa	June	gs = 0.36exp(−0.5(ln(D/1.6)/0.99)^2)	0.968	1.60	64.11	1.43	25.8
	August	gs = 0.29exp(−0.5(ln(D/1.74)/0.71)^2)	0.901	1.74	60.45	0.61	25.1
	October	gs = 0.31exp(−0.5(ln(D/1.25)/0.64)^2)	0.838	1.25	56.59	0.78	15.3

Figure 5. The concentration of abscisic acid (ABA) and the sensitivity of stomatal conductance (g_s) to vapor pressure deficit (VPD) in the three trees in different seasons in Jinan. The sensitivity of g_s to VPD is described by Root Mean Square Error (RMSE, σ, n = 9).