Detection of responses to drought stress of dalbergia cochinchinensis seedlings using the physiological parameters and thermal imaging

Figures & data

Figure 1. The daily change of soil moisture of seedlings in different drought stress periods.

Table 1. Summary of treatment and growth condition of D. cochinchinensis seedlings.

Days of Drought	Before Drought		After Drought		Chamber Temperature (°C)		Related Humidity (RH %)
	Pot weight (Kg)	Soil moisture (VWC m^3/m^3)	Pot weight (Kg)	Soil moisture (VWC m^3/m^3)	Day	Night	Day	Night
D5	2.40	0.31	2.14	0.29	19–22	10–12	70–80	84–97
D8	2.38	0.32	1.94	0.23
D11	2.48	0.32	1.90	0.21
D14	2.44	0.34	1.82	0.20

Table 2. Mean different and standard deviation of minimum fluoresence (Fo), maximum fluoresence (Fm) and maximal PS II photochemical efficiency (Fv/Fm) before and after different drought stress period compared by paired t-test.

Measurement	Before and After Drought	Days of Drought
		D5	D8	D11	D14
Fo	Before-D	5212.30 ± 813.46 b	6445.30 ± 754.74 a	4766.30 ± 387.17 b	6450.30 ± 1014.06 a
	After-D	6699.46 ± 179.68 a	6111.96 ± 420.13 a	6414.28 ± 393.25 a	6980.68 ± 642.05 a
Fm	Before-D	19080.60 ± 3415.94 b	24168.50 ± 1453.20 a	20494.00 ± 2144.56 a	26923.40 ± 2884.62 a
	After-D	23595.02 ± 863.98 a	22015.94 ± 2091.95 a	22225.01 ± 1384.88 a	24396.04 ± 1906.35 b
Fv/Fm	Before-D	0.724 ± 0.015 a	0.733 ± 0.024 a	0.766 ± 0.022 a	0.760 ± 0.015 a
	After-D	0.707 ± 0.012 b	0.714 ± 0.032 b	0.708 ± 0.012 b	0.709 ± 0.010 b

In each column, Values represent different means ± standard deviation. Different letter(s) are indicated significantly different at p < 0.05 confidence interval for mean difference compared by paired t-test.

Table 3. Mean different and standard deviation of Chlorophyll content of seedlings before and after different drought stress period compared by paired t-test.

Days of Drought	Chlorophyll Content (SPAD Unit)
	Before	After
D5	31.84 ± 5.18 a	28.22 ± 3.25 a
D8	35.92 ± 6.37 a	30.79 ± 3.43 b
D11	33.68 ± 4.25 a	32.30 ± 3.78 a
D14	33.40 ± 6.81 a	28.42 ± 3.72 b

In each column, Values represent different means ± standard deviation. Different letter(s) are indicated significantly different at p < 0.05 confidence interval for mean difference compared by paired t-test.

Table 4. Mean different and standard deviation of Transpiration rate (E), Stomatal conductance (gs), Net photosynthetic rate (A) and Water use efficiency (WUE) before and after different drought stress period compared by paired t-test.

Measurement	Before and After Drought	Days of Drought
		D5	D8	D11	D14
E (mmol m^−2 s^−1)	Before-D	2.08 ± 0.71 a	1.94 ± 0.54 a	2.11 ± 0.63 a	1.23 ± 0.43 a
	After-D	1.82 ± 0.35 a	1.19 ± 0.16 b	1.13 ± 0.31 b	0.85 ± 0.17 a
gs (mmol m^−2 s^−1)	Before-D	251.77 ± 106.56 a	271.90 ± 36.21 a	225.64 ± 19.13 a	168.16 ± 40.70 a
	After-D	197.72 ± 97.94 a	233.80 ± 33.95 b	194.44 ± 21.80 b	124.06 ± 26.33 b
A (µmol m^−2 s^−1)	Before-D	4.56 ± 0.98 a	3.22 ± 1.04 a	3.54 ± 0.92 a	2.09 ± 0.58 a
	After-D	3.44 ± 0.93 b	2.27 ± 0.62 b	2.52 ± 0.95 b	1.58 ± 0.40 b
WUE (µmol mmol^−1 m^−2 s^−1)	Before-D	1.90 ± 0.32 a	1.49 ± 0.58 a	1.34 ± 0.26 b	1.45 ± 0.53 b
	After-D	1.99 ± 0.54 a	1.95 ± 0.39 a	2.46 ± 0.50 a	1.89 ± 0.40 a

In each column, Values represent different means ± standard deviation. Different letter(s) are indicated significantly different at p < 0.05 confidence interval for mean difference compared by paired t-test. E : Transpiration rate, gs : Stomatal conductance, A : Net photosynthesis rate, WUE : Water use efficiency.

Table 5. Mean different and standard deviation of leaf temperature of seedlings before and after drought stress at different period compared by paired t-test.

Leaves Position	Before and After Drought	Leaf Temperature (°C)
		Days of Drought
		D5	D8	D11	D14
Upper	Before	22.22 ± 0.22 b	23.38 ± 0.56 b	27.82 ± 3.37 a	24.70 ± 0.83 b
	After	29.15 ± 0.62 a	31.14 ± 0.69 a	29.33 ± 0.80 a	30.61 ± 0.76 a
Middle	Before	22.28 ± 0.21 b	23.33 ± 0.52 b	27.66 ± 3.01 a	24.60 ± 0.73 b
	After	28.10 ± 0.70 a	29.53 ± 0.67 a	28.13 ± 0.65 a	29.26 ± 0.51 a
Bottom	Before	22.34 ± 0.23 b	23.32 ± 0.48 b	27.34 ± 2.94 a	24.48 ± 0.66 b
	After	27.17 ± 0.39 a	28.26 ± 0.44 a	27.36 ± 0.50 a	28.03 ± 0.53 a

In each column, Values represent different means ± standard deviation. Different letter are indicated significantly different at p < 0.05 confidence interval for mean difference compared by paired t-test.

Figure 2. Visual and thermal image of D. cochinchinensis seedlings over the drought period 14 days. (a), (b) (c) visual image and (d), (e), (f) Thermal image at day before drought, drought at day 3 and drought at day 14.