Capitulum
and floret primordia development in plants of sunflower
(helianthus annuus l.) treated with the morphactin chlorflurenol
Introduction:
"Many
theories to explain the generation of floret pattern in capitula
of Compositae have been developed (Schwabe, 1984; Hernández,
1988; Green, 1991; Hernández and Green, 1993; Jean, 1994).
Nevertheless the processes involved in the differentiation and
pattern generation of floret primordia are not yet well
understood. This paper reports the changes produced in the floret pattern in
the capitulum of sunflower using the morphactin Chlorflurenol
(CF1: 2-Chloro-9-Hydroxy-fluorene-9-Carboxylic acid) which main
action, produced by the inhibition of IAA transport (Noodén and
Noodén, 1985), is the reduction of meristematic growth
(Schneider, 1970)".
Author:
Luis F. Hernández. V Interamerican Electron Microscopy
Congress, Venezuela, 24-28 October 1999. Source: The Sunflower-Girasol
site of Luis F. Hernández.
Colchicine-induced
displacement of floral organ regeneration sites in the wounded
sunflower capitulum
Abstract:
“As previously described a circular wounding procedure as
applied to the young capitulum of the sunflower to isoalte a 1 mm
diameter cylindrical plug of receptacle tissue in situ and
stimulate the recapitulation on the plug surface of involucral
bracts, ray and disc floret initials. Applying 4,4 mM
colchicine to the wounded wall of the plug for 5 days,
subsequently resulted in a collar of meristematic-like cells
forming 20-50 um from the wound site folled by the appearance of
floral initials on the inside of the collar, 100-120 um distance
from the plug wall, demonstrating that dedifferentation and
regeneration processes are not confined to the plug rim".
Author:
Luis F. Hernández and J. H. Palmer.
Published in:
Micr. Electr. Biol. Cel. (ISSN 0326-3142), vol. 14:
159-164, 1990, nº 2.
Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Effect
of foliar applications of methanol on growth and yield of
sunflower (Helianthus annuus L.)
Abstract:
“The effect of foliar applied methanol (Met) on growth and
development of sunflower (Helianthus annuus L.) plants, grown
under controlled conditions or in the field, was studied.
Foliar sprays of aqueous (30%, v/v) Met were applied at the
beginning of capitulum development (23 days from seedling
emergence, DFE), and every 4 days up to 41 DFE, when the floret
primordia were completely differentiated on the capitulum surface.
Met treated plants grown under controlled conditions showed
significant channges in vegetative growth and floral development.
Met increased stem length by 23.6%, leaf area per plant by
66.5, stem dry weight by 51.4%, number of floret primordia by
46.5% and accelerated completion of floral development by 4.5
days.
Met treated plants grown in the field did not show
significant changes compared with controls, except subtle
differences in vegetative development viusally detected in leaf
turgor and leaf color 5 days after the treatment commenced, but
these changes were not statistically significant".
Authors:
L.F. Hernández, C.N. Pellegrini, L. M. Malla. Published in: fYTON,
International Journal of Experimental Botany. Vol. 66: 1-8,
2000. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Floret
differentiation in the capitulum of sunflower (Helianthus annuus
L.)
Abstract:
“In the capitulum of sunflower the process of generation of new
floret primordia starts at the receptacle rim and continues
towards its center.
Then, each floret primordium differentiates gradually over
space and time, in the centripetal direction.
The florets appear in an annular generative zone first as a
gentle dome and then become a two-part structure: the floret bract
and the floret corolla.
This paper provides a detailed description of the beginning
of the floret primordium differentiation during the floral
morphogenetic process in the sunflower capitulum”.
Author:
Luis F. Hernández. Published in: Helia vol. 20: 63-68,
1997, nº 26. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Floret
primordia differentiation in naturally wounded capitula of boron
deficient sunflower (helianthus annuus l.) plants
Introduction:
"Boron
deficiency during floret intiation in sunflower results in damage
of capitulum meristem and consequently in the appeareance of
involucral bracts and ray florets in different positions at the
capitulum centre (Blamey, 1976, Palmer and Marc, 1982).
Palmer and Marc (1982) reported this effect after pin prick
wounding of the uncomitted receptacle surface in Floral Stage (FS)
4, 5 or 6 (Marc and Palmer, 1981). They concluded that the wound
rims could provide the first sites for organ initials (Palmer and
Marc, 1982, Hernández and Palmer, 1988). This paper provides a
detailed sequential description of floret primordia
differentiation on naturally wounded capitula from boron-deficient
sunflower plants. The implications of findings presented here for
organogenesis of the sunflower capitulum, have been extensively
discussed (Hernández, 1988; Hernández and Palmer, 1988,1991;
Hernández and Green, 1993)".
Author:
Luis F. Hernández. V Interamerican Electron Microscopy
Congress, Venezuela, 24-28 October 1999. Source: The Sunflower-Girasol
site of Luis F. Hernández.
volver
arriba
Grain
yield of the sunflower capitulum promoted by surgical removal of
the involucral bract primordia
Abstract:
“This paper reports the effect on the sunflower capitulum
development and seed yield of removing the involucral bract (IB)
primordia and upper leaf primordia during early growth of the
capitulum.
Plants of sunflower cv. Dekalb G100, were used grown in a
controlled environment and in the field.
As a result of IB and/or upper leaves removal, the rate of
floral development and the size of the treated capitula, increased
significantly in both experiments.
The total number of disc floret primordia also increased
significantly by up to 21.5 %.
The absence of IB during capitulum formation produced a
significant increase in capitulum size and promoted grain yield
measured on per plant basis.
It is concluded that the growth of the receptacle in the
sunflower capitulum is highly dependent of the supply of
photoassimilates coming from older mature non-growing leaves and
that the younger leaves which are expanding at the time of
capitulum formation and the involucral bract primordia can
produced strong competition for assimilates that can result in a
reduction in the potential size of the capitulum”.
Author:
Luis F. Hernández. Published
in: Soil Science (Trends in Agril. Sci.) vol. 1, 127-135, 1993.
Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Imbibition
and germination rates of sunflower (Helianthus annuus L.) seeds
according to fruit size
Abstract:
"The
influence of size and pericarp structure of sunflower (Heliathus
annuus L.) fruits on imbibition and germination rates of the seed
was investigated. The results show a positive correlation
between fruit width, pericarp thickness and fruit weight.
Germination rate was not affected by fruit size.
Nevertheless, although large fruits (more than 4.5 mm width) have
a rapid imbibition rate there was a significant lag in the start
of their germination in relation to that of the smaller fruits
(less than 2.5 mm width)".
Authors:
Luis F. Hernández and Gustavo A. Orioli. Published in:
Field Crops Research, vol. 10: 355-360, 1985. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Morphogenesis
in sunflower (Helianthus annuus L.) as affected by exogenous
application of plant growth regulators
Abstract:
“The effect of the plant growth regulators (PGRs)
N6-benzyladenine (BA), a-Naphthaleneacetic acid (NAA) and
Gibberellic acid (GA3) on morphogenesis of sunflower (Helianthus
annuus L.) was studied. PGRs were applied at the beginning
of capitulum development, where floret primordia were still not
determined, at dosis of 45mg of NAA day-1 during 10 days, or
45mg of BA day-1 during 10 days, or 45mg of GA3 day-1 during 5
days. Compared with untreated plants, NAA was not able to
produce any significant change. GA3 was effective
increasing the length of stem internodes and accelerating the
onset of floral development by 25.0%. BA showed the most
significant effect on plant development, increasing the leaf
area per plant by 38.0%, the stem dry weight by 93.0% and
changing capitulum morphology and hence disc floret development.
BA-treated plants showed an increase in the numbber of floret
primordia of 17.0% associated with a significant promotion of
the receptacle expansion before the beginning of the floret
differentiation period".
Author:
L. F. Hernández.
Pubished in: Agriscientia,
vol. XIII: 3-11, 1996. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
Morphological
changes in the epidermis of sunflower (helianthus annuus l.)
leaves induced by uv radiation
Introduction:
"UV radiation can affect growth, productivity and yield of
different crop plants. Changes in the morphology, anatomy and
development of UV exposed plants as well as the reduction of the
leaf photosynthetic efficiency have been reported (Teramura and
Sullivan, 1994). The sunflower shows tolerance to low doses
of UV-B radiation (Barnes et al., 1990). Nevertheless alterations
in its leaf morphology and reproductive pattern in southern
Argentina have been associated with recent increases in the levels
of UV-B (Sunflower Breeders, pers. comm.). Previous observations
using light microscopy (Hernández et al., 1999) revealed some
alterations at epidermal level and in the internal structure of
leaves (changes in the size and morphology of chloroplasts). The
objective of this work was to study the morphology of the leaf
surface of sunflower plants exposed to UV-A+B radiation using
scanning electron microscopy (SEM)".
Authors:
L.F. Hernández, L.I. Lindström and C.N. Pellegrini.
V
Interamerican Electron Microscopy Congress, Venezuela, 24-28
October 1999. Source: The Sunflower-Girasol
site of Luis F. Hernández.
Regeneration
of the sunflower capitulum after cylindrical wounding of the
receptacle
Abstract:
“Using the young capitulum of Helianthus annuus L., a
cylindrical plug of undifferentiated receptacle tissue, 1 mm in
diameter, was isolated from lateral communication with the rest of
the receptacle surface by a vertical circular wound cut, while
retaining continuity with the subapical meristerm. Within 24
hr., active cell division was induced at the inner and outer
surfaces of the wound and in the receptacle epidermis bordering
the wound edges, creating a rounded rim at the top of the wound.
Within 3-6 days, floral initials, spaced 133-166 mm
apart appeared on the flanks of both rims and later on the top of
the plug and surrounding receptacle surface. The first
formed initials developed into involucral bracts or ray florets
and the later ones into disc florets which were organized into
contact parastichics, the number of which did not conform with the
Fibonacci series. The base of the plug developed into a
stem-like structure completing the regeneration of a fully formed
functional capitulum. This operation was demonstrated for
two sunflower cultivars and occurred in both long and short
daylengths".
Authors:
Luis. F. Hernández and John H. Palmer.
Published in: Amer. J. Bot. Vol. 75: 1253-1261, 1988, nº
9. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
volver
arriba
Transductions
for the expression of structural pattern: Analysis in sunflower
Abstract:
“The transductions to initiate and propagate pattern were
investigated in the sunflower head. The spiral pattern
emerges as new florets form in regular centripetal sequence on the
flat disc. The spiral lines of florets arise as rows of
simple bumps. Each bump splits to become a small bract and a
circular disc flower. This topographical progression was
described by a scanning electron microscopic technique applied to
living tissue. The suitability of various theories to
explain the progression was examined. Because no periodic
cell specialization was seen by scanning electron microscopy prior
to pattern emergence, a mechanism that produces pattern in uniform
tissue by spontaneous physical buckling (folding) was examined
further. Key configurational changes of development were
reproduced in models using the buckling assumptions. In
further testing, a young head was physically constrained to cause
it to grow as an oval. Pattern was modified as predicted.
Unexpectedly, organ character changed as well. In localized
regions, the folding was abnormal; the typical dyad floret, bract
and flower, was replaced by a single large bract. This
anomally is known in mutants of sunflower; hence, the physical
treatment induced a phenocopy. We concluded that (1)
buckling is a strong candidate to be the process producing organ
pattern, and (2) the accompanying topographical changes can be
prerequisite to organ differentiation".
Authors:
Luis F. Hernández and Paul B. Green.
Published in: The Plant Cell
vol.5: 1725-1738, 1993. Source: The Sunflower-Girasol
site of Luis F. Hernández. Find the complete paper down "some of my papers".
volver
arriba
Volver
a Temas AgrícolaS EN INGLES
Volver
a la Página Principal |
