Proline and antioxidant enzymes protect <i>Tabebuia aurea</i> (Bignoniaceae) from transitory water deficiency

Freire, Fátima Conceição de Jesus; Silva-Pinheiro, Juliana da; Santos, Jayne Silva; Silva, Arthur Gomes Lima da; Camargos, Liliane Santos de; Endres, Lauricio; Justino, Gilberto Costa

doi:10.1590/2175-7860202273031

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Original Paper • Rodriguésia 73 • 2022 • https://doi.org/10.1590/2175-7860202273031 copy

Proline and antioxidant enzymes protect Tabebuia aurea (Bignoniaceae) from transitory water deficiency

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Abstract

Water deficiency is a major abiotic stress that limits biomass production and drives plant species distributions. We evaluate the effects of water deficiency on ecophysiological and biochemical parameters of seedlings of Tabebuia aurea. Plants were subjected to daily watering (control) and to stress by soil water deficiency for 29 days. Leaf area, plant biomass, gas exchange, SPAD index, maximum quantum yield (F_v / F_m ), quantum yield of PSII (ΦPSII), superoxide dismutase (SOD) and L-ascorbate peroxidase (APX) activity, lipid peroxidation, and proline content were recorded. Plants responded to water deficit by reducing leaf area and accumulating proline. Stomatal conductance was reduced to limit the water loss by transpiration. However, limiting CO₂ uptake caused reduction in photosynthesis and biomass. The excess of energy unutilized by photosynthesis reduced SPAD index and ΦPSII. As a result, we observed an increase in SOD and APX activity, protecting chloroplast membranes from further damages caused by lipid peroxidation. Our results indicate that T. aurea have capacity to survive under water deficiency reducing stomatal aperture, but affecting the rate of CO₂ assimilation. Nevertheless, plants showed mechanisms to preventing damages to the photosynthetic apparatus. Such plasticity is an important adaptation for plants growing in dry environmental.

Key words
antioxidant system; gas exchange; tree species; water deficit; proline

Parameter	Control ± SD	Water deficit ± SD
g_s (mol H₂O m^-2 s^-1)	0.07 ± 0.006	0.006 ± 0.002*
E (mmol H₂O m^-2 s^-1)	3.78 ± 0.3	0.37 ± 0.1*
A (µmol CO₂ m^-2 s^-1)	8.53 ± 0.67	1.27 ± 0.34*
iWUE (µmol CO₂ mmol H₂O^-1)	2.25 ± 0.1	3.42 ± 0.89*
IWUE (µmol CO₂ mol H₂O^-1)	116.7 ± 6.07	206.3 ± 24.8*

	Ψw _leaf	Pro	Ψw _soil	SPAD	F _v / F _m	SOD	APX	MDA	A	g _s	E
	Control treatment
Ψw_leaf	---	0.10	0.78	-0.53	-0.55	-0.07	0.72	-0.71	-0.71	0.05	0.11
Pro	-0.89*	---	0.02	-0.88*	-0.59	-0.62	-0.48	-0.29	-0.59	-0.41	-0.39
Ψw_soil	0.41	-0.12	---	-0.31	-0.44	-0.22	0.59	-0.28	0.04	0.59	0.61
SPAD	0.31	-0.23	0.68	---	0.66	0.43	0.43	0.67	0.67	0.36	0.30
F _v / F _m	0.64	-0.58	0.55	0.90*	---	0.85	0.18	0.15	0.81	0.36	0.38
SOD	-0.44	0.35	0.38	0.21	-0.16	---	0.59	-0.32	0.56	0.23	0.30
APX	0.67	-0.88*	-0.35	-0.08	0.33	-0.59	---	-0.60	0.22	0.42	0.50
MDA	-0.45	0.15	0.00	0.37	0.09	0.76	-0.21	---	0.37	0.22	0.11
A	0.37	-0.20	-0.30	-0.63	-0.30	-0.78	0.38	-0.93*	---	0.82	0.81
g _s	0.23	-0.19	-0.42	-0.85	-0.56	-0.51	0.38	-0.72	0.90*	---	0.99**
E	0.24	-0.20	-0.43	-0.84	-0.55	-0.52	0.39	-0.72	0.91*	0.99*	---
	Water deficit treatment

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[1] 11Author for correspondence: gilberto.justino@icbs.ufal.br