Lower oxidative damage and cell wall loosening, mediated or not by auxin, as part of the tolerance mechanism of <i>Paubrasilia echinata</i> morphotypes in the shade and full sun

Gama, Vinícius Novo; Zanetti, Leonardo Valandro; Macieira, Bernardo Pretti Becacici; Cuzzuol, Geraldo Rogério Faustini

doi:10.1590/0102-33062020abb0504

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Article • Acta Bot. Bras. 35 (4) • Oct-Dec 2021 • https://doi.org/10.1590/0102-33062020abb0504 copy

Lower oxidative damage and cell wall loosening, mediated or not by auxin, as part of the tolerance mechanism of Paubrasilia echinata morphotypes in the shade and full sun

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ABSTRACT

Paubrasilia echinata presents three morphotypes that differ from each other in leaf morphology (small morphotype-SM, medium morphotype-MM, and large morphotype-LM) with indications of divergence between them regarding irradiance tolerance. The present study aimed to identify possible physiological and growth patterns in P. echinata morphotypes under contrasting irradiance. The growth and photosynthesis of SM were inhibited in the full sun, and those of MM and LM, in the shade. The auxin contents of the three morphotypes increased in the full sun. However, in MM and LM, this increase was 5 times greater. The oxidative damage (hydrogen peroxide-H₂O₂ and lipid peroxidation-MDA content) of SM were higher in the full sun and of MM and LM in the shade. The stem hemicelluloses and CO₂ assimilation decreased in shade for SM, and sun for MM and LM. The shade tolerance of SM and the full sun tolerance of MM and LM were associated with lower oxidative damage and cell wall loosening (lower hemicelluloses content) in the photo-promoted treatments. The integration of the lower oxidative damage with cell wall loosening seems to represent an essential part of the tolerance mechanism of P. echinata morphotypes in the shade and full sun.

Keywords:
auxin; Brazilwood; hemicelluloses; oxidative stress; photo-assimilation

deep (cm)	sand	silt %	clay	C g kg^-1	N g kg^-1	C/N	pH	SEB cmolc kg^-1	CEC cmolc kg^-1	V %	P mg kg^-1
0-11	91	4	5	0.90	0.07	12.9	5.3	2.6	4.2	62	2
11-41	79	5	16	0.60	0.07	8.6	5.2	1.5	3.6	42	2

Variables	Category	Morphotypes
Variables	Category	Small	Medium	Large
High	Growth	0.2^c	0.4^b	0.6^a
TDM		0.4^b	0.9^a	0.9^a
R:S		0.5^b	0.7^a	0.5^b
LMA		0.6	0.6	0.6^n.s.
RGR		0.1^c	0.4^b	0.6^a
NAR		0.5^b	0.7^a	0.8^a
A		0.4^b	0.6^a	0.7^a
Ci		0.2	0.1	0.2^n.s.
E		0.2^b	0.4^a	0.5^a
gs	Photosynthesis	0.5	0.5	0.4 ^n.s.
WUE		0.2^b	0.3^ab	0.4^a
Φc		0.2^b	0.6^a	0.6^a
F_V /F _M		0.3^a	0.0^b	0.0^b
Rd		0.6^a	0.3^b	0.1^c
IAA		0.2^b	0.8^a	0.9^a
H₂O₂		0.8^a	0.4^b	0.3^b
MDA		0.8^a	0.7^ab	0.6^b
Cel. leaf	Biochemical	0.2	0.2	0.3^n.s.
Cel. stem		0.1	0.1	0.1^n.s.
Hem. leaf		0.2	0.3	0.2^n.s.
Hem. stem		0.1	0.1	0.1^n.s.
Lig. leaf		0.2	0.3	0.2^n.s.
Lig. stem		0.1	0.1	0.2^n.s.

Sociedade Botânica do Brasil SCLN 307 - Bloco B - Sala 218 - Ed. Constrol Center Asa Norte CEP: 70746-520 Brasília/DF. - Alta Floresta - MT - Brazil
E-mail: acta@botanica.org.br

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[1] * Corresponding author: bernardopretti@gmail.com