Open Access
ARTICLE
Biomechanical proposal as a cause of incomplete seed and pericarp development of the sunflower (Helianthus annuus L.) fruits
Hernández LF1,2, PM Bellés3, MA Bidegain4,5, PD Postemsky4
1 Laboratorio de Morfología Vegetal. Departamento de Agronomía, Universidad Nacional del Sur (UNS), 8000 Bahía Blanca.
2 Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), 1900 La Plata.
3 Depto. de Ingeniería, UNS, 8000 Bahía Blanca.
4 Centro de Recursos Renovables de la Zona Semiárida (CERZOS), UNS, CONICET, Lab. de Biotecnología de Hongos Comestibles y Medicinales, 8000 Bahía Blanca.
5 Departamento de Biología, Bioquímica y Farmacia, UNS, 8000 Bahía Blanca. Argentina.
Address correspondence to: Luis F. Hernández, e-mail:
Phyton-International Journal of Experimental Botany 2018, 87(all), 198-208. https://doi.org/10.32604/phyton.2018.87.198
Abstract
Absence or underdevelopment of sunflower fruits
come usually from failure in fertilization, stresses as well as physiological
and morphological defects in the ovary. Thigmomorphogenesis
has never been included as a possible cause. We have previously
shown that a 2-3 day fertilization shift can occur between neighboring
florets in the sunflower capitulum. It is proposed here that
those ovaries with advanced fertilization can generate a significant
radial and axial compressive stress on ovaries with delayed fertilization.
This mechanical stimulus could be strong enough to trigger a
thigmo response that affects further ovary development. In vivo tests
were performed, isolating ovaries by removing the adjacent flowers
and rubbing them several times using a micromanipulator applying a
force of 1 to 3 N. Total peroxidases in treated and untreated ovaries,
isolated and not isolated were measured 24 h after treatments. Ovary
development was studied in control and isolated flowers, both rubbed
and not rubbed. Also a mechanical a model was made to simulate the
mechanical behavior of an ovary surrounded by advanced growing
neighboring ovaries. A meshed 3-D model of a young ovary was
constructed and a computer simulation was performed using finite
element analysis. Shear stresses generated by the friction of neighboring
ovaries in contact with the model, fertilized three days later,
were then estimated. After rubbing, isolated ovaries in planta showed
a thigmo response that resulted in empty or incompletely developed
fruits. Total peroxidase levels (ΔAbs
470 min
-1.g fresh weight
-1) rose
from 22 in control ovaries to 72 in rubbed ones. The number of
ovaries that did not develop any seed from these incompletely developed
fruits rose from 16.2 to 20.0% in the control non-isolated
flowers to 61.1 to 86.7% in the rubbed ovaries, but dropped to 6.7
to 7.3% in the non-rubbed but isolated ovaries. From the simulation
it was found that the area of contact with the receptacle was prone to show a higher magnitude of stress after deformation induced by
shear forces generated by neighboring ovaries. Thigmomorphogenesis
can also explain the failures observed at early stages of the sunflower
ovary development. The ovary tissue sensitivity at this stage
could contribute to the rapid response of the mechanically generated
stimulus between neighbouring ovaries.
Keywords
Cite This Article
LF, H., Bellés, P., Bidegain, M., Postemsky, P. (2018). Biomechanical proposal as a cause of incomplete seed and pericarp development of the sunflower (
Helianthus annuus L.) fruits.
Phyton-International Journal of Experimental Botany, 87(all), 198–208. https://doi.org/10.32604/phyton.2018.87.198