PHOTOSYNTHETIC TRAITS OF CANOPY LEAVES OF DINIZIA EXCELSA (FABACEAE)

Mendes, Keila Rêgo; Bento, Marcos; Marenco, Ricardo Antonio

doi:10.1590/1806-90882019000400009

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ARTICLE • Rev. Árvore 43 (4) • 2019 • https://doi.org/10.1590/1806-90882019000400009 copy

PHOTOSYNTHETIC TRAITS OF CANOPY LEAVES OF DINIZIA EXCELSA (FABACEAE)

CARACTERÍSTICAS FOTOSSINTÉTICAS DE FOLHAS DE DOSSEL DE DINIZIA EXCELSA (FABACEAE)

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The response of leaf traits to irradiance and [CO₂] in canopy leaves of several tall trees remains to be determined under natural conditions. Thus, the objective of this work was to determine gas-exchange parameters in sun and shade leaves of Dinizia excelsa Ducke in 35-45 m tall trees of Central Amazonia. We assessed light saturated photosynthesis (A_max), stomatal conductance (g_s), mesophyll conductance (g_m), transpiration rates (E), water use efficiency (WUE), intrinsic water use efficiency (WUEi), maximum electron transport rate (J_max), the maximum carboxylation rate of Rubisco (V_cmax), intercellular CO₂ concentration (C_i)specific leaf area (SLA) and fresh leaf thickness. We also estimated the CO₂ concentration at the chloroplast level (C_c) and determined the light and CO₂ saturated photosynthesis (A_pot). A_max was obtained at light saturation (1200 µmol m^-2 s^-1), whereas A_pot, V_cmax, J_max and g_m were obtained after constructing A/C_i response curves. There was a significant difference between sun and shade leaves in C_i and C_c, but for other parameters no differences were observed. A_max was positively correlated with g_s, g_m and E, and there was also a significant correlation between g_s and gm (p ≤ 0.05), as well as between J_max and V_cmax. Thicker leaves had higher values of A_max, g_s, C_i, C_c and E. A_pot was limited by the electron transport rate and by low g_m. The canopy of the tree caused a decrease in irradiance (30-40%), but this reduction was not enough to reduce important photosynthetic parameters. Thus, all resources allocated to leaf production led to maximum use of the solar energy received by the leaves, which allowed this species to grow at fairly rapid rates.

Keywords:
Mesophyll conductance; Maximum carboxylation rates of Rubisco; Central Amazonia

Table 1 Light saturated photosynthesis (Amax), light and CO2 saturated photosynthesis (Apot), stomatal conductance (gs), mesophyll conductance (gm), intercellular CO2 concentration (Ci), chloroplast CO2 concentration (Cc), vapor pressure deficit (VPD), leaf temperature (Tleaf), water use efficiency (WUE), intrinsic water use efficiency (WUEi), the maximum carboxylation rate of Rubisco (Vcmax), electron transport rate (Jmax), Fv/Fm ratio, specific leaf area (SLA), chlorophyll content, SPAD values, fresh leaf thickness (FLT), and absolute chlorophyll content (a, b and a + b) in sun and shade leaflets of Dinizia excelsa. Different capital letters denote significant differences (p = 0.05, t-test) between the canopy strata (sun and shade leaflet). Each value represents the mean (± SE) of six trees and two leaflets per tree.

PARAMETER	SUN LEAFLET	SHADE LEAFLET
A_max (µmol m^-2 s^-1)	8.7 ± 1.3 A	5.9 ± 0.7 A
A_pot (µmol m^-2 s^-1)	24.1 ± 4.0 A	19.3 ± 2.1 A
g_s (mol m^-2s^-1)	0.13 ± 0.03 A	0.07 ± 0.02 A
g_m (mol m^-2 s^-1 bar^-1)	0.07 ± 0.009 A	0.05 ± 0.005 A
C_i (µmol mol^-1)	232.6 ± 11.4 A	201.8 ± 11.6. B
C_c (µmol mol^-1)	107.9 ± 5.3 A	93.8 ± 5.4 B
V_cmax (µmol m^-2 s^-1)	41.1 ± 4.9 A	38.4 ± 3.3 A
J_max (µmol m^-2 s^-1)	101.2 ± 14.6 A	80.6 ± 8.3 A
VPD (kPa)	1.8 ± 0.2 A	1.9 ± 0.2 A
T_leaf (ºC)	33.4 ± 0.8 A	33.6 ± 0.8 A
WUE (mmol mol^-1)	4.4 ± 0.6 A	5.2 ± 0.2 A
WUE_i (µmol mol^-1)	76.4 ± 9.5 A	108.3 ± 13.3 A
F_v/F_m (unitless)	0.78 ± 0.005 A	0.78 ± 0.005 A
SLA (m² kg^-1)	7.8 ± 0.5 A	7.5 ± 0.4 A
FLT (mm)	0.20 ± 0.003 A	0.16 ± B
SPAD	68.1 ± 4.4 A	57.2 ± 3.7 A
Chlorophyll a (µmol m^-2)	362.1 ± 42.7 A	317.6 ± 19.4 A
Chlorophyll b (µmol m^-2)	93.6 ± 26.0 A	98.1 ± 19.3 A
Chlorophyll a+ b (µmol m^-2)	470.8 ± 39.9 A	415.7 ± 27.9 A

Table 2 Pearson's correlation matrix between light saturated photosynthesis (Amax), light and CO2 saturated photosynthesis (Apot), stomatal conductance (gs), mesophyll conductance (gm), intercellular CO2 concentration (Ci), chloroplast CO2 concentration (Cc), transpiration (E), vapor pressure deficit (VPD), leaf temperature (Tleaf), water use efficiency (WUE), intrinsic water use efficiency (WUEi), the maximum carboxylation rate of Rubisco (Vcmax), electron transport rate (Jmax), specific leaf area (SLA), fresh leaf thickness (FLT) in Dinizia excelsa. *: significant (p ≤ 0.05); **: significant (p ≤ 0.01), ns: not significant (p > 0.05).

Parameter	A _max	A _pot	g _s	g _m	C _i	C _c	E	VPD	T _leaf	WUE	WUE_i	V _cmax	J _max	SLA	FLT
A _max	-	0.75**	0.95**	0.96**	0.66**	0.66**	0.92**	-0.52**	-0.32*	-0.28*	-0.70**	0.82**	0.81**	-0.05ns	0.34*
A _pot	0.75**	-	0.60**	0.82**	0.30*	0.30*	0.74**	-0.12ns	-0.03ns	-0.21ns	-0.35*	0.73**	0.97**	-0.30*	0.08ns
g _s	0.95**	0.60**	-	0.83**	0.78**	0.78**	0.90**	-0.65**	-0.46*	-0.30*	-0.77**	0.65**	0.63**	0.1ns	0.46*
g _m	0.96**	0.82**	0.83**	-	0.42*	0.42*	0.85**	-0.37*	-0.20ns	-0.15ns	-0.49*	0.92**	0.89**	-0.18ns	0.20ns
C _i	0.66**	0.30*	0.78**	0.42*	-	1.0**	0.74**	-0.60**	-0.38*	-0.59**	-0.96**	0.21ns	0.32*	0.24ns	0.52**
C _c	0.66**	0.30*	0.78**	0.42*	1.0**	-	0.74**	-0.60**	-0.38*	-0.59**	-0.96**	0.21ns	0.32*	0.24ns	0.52**
E	0.92**	0.74**	0.90**	0.85**	0.74**	0.74**	-	-0.34*	-0.08ns	-0.57**	-0.79**	0.67**	0.79**	-0.19ns	0.38*
VPD	-0.52**	-0.12ns	-0.65**	-0.37*	-0.60**	-0.60**	-0.34*	-	0.92**	-0.29*	0.42*	-0.2ns	-0.08ns	-0.63**	-0.43*
T _leaf	-0.32*	-0.03ns	-0.46*	-0.20ns	-0.38*	-0.38*	-0.08ns	0.92**	-	-0.49*	0.18ns	-0.10 ns	0.05ns	-0.76**	-0.40*
WUE	-0.28*	-0.21ns	-0.30*	-0.15ns	-0.59**	-0.59**	-0.57**	-0.29*	-0.49*	-	0.73**	-0.07ns	-0.29*	-0.39*	-0.19ns
WUE_i	-0.7**	-0.35*	-0.77**	-0.49*	-0.96**	-0.96**	-0.79**	0.42*	0.18ns	0.73**	-	-0.31*	-0.41*	-0.04ns	-0.43*
V _cmax	0.82**	0.73**	0.65**	0.92**	0.21ns	0.21ns	0.67**	-0.2ns	-0.10 ns	-0.07ns	-0.31*	-	0.81**	-0.33*	0.09ns
J _max	0.81**	0.97**	0.63**	0.89**	0.32*	0.32*	0.79**	-0.08ns	0.05ns	-0.29*	-0.41*	0.81**	-	-0.36*	0.09ns
SLA	-0.05ns	-0.30*	0.10ns	-0.18ns	0.24ns	0.24ns	-0.19ns	-0.63**	-0.76**	-0.39*	-0.04ns	-0.33*	-0.36*	-	0.58**
FLT	0.34*	0.08ns	0.46*	0.20ns	0.52**	0.52**	0.38*	-0.43*	-0.40*	-0.19ns	-0.43*	0.09ns	0.09ns	0.58**	-

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