TY - JOUR
T1 - Solute permeation across the apoplastic barrier in the perisperm-endosperm envelope in cucumber seeds
AU - Amritphale, Dilip
AU - Ramakrishna, P.
AU - Singh, Bharat
AU - Sharma, Santosh K.
PY - 2010
Y1 - 2010
N2 - An apoplastic barrier consisting of callose and lipid layers in the perisperm-endosperm (PE) envelope is known to restrict inward and outward transport of solutes in cucurbit seeds. The present work examines permeability properties of the barrier using cucumber seed as a model system. Osmometrically determined osmotic potential of the apoplastic fluid was used as a basis for osmotic studies aimed at examining solute exclusion from the apoplastic barrier in the PE envelope. The assessment of apoplastic permeability involved measuring the amount of anionic and cationic organic dyes diffused into agarose gel discs through the PE envelope. Ionic/non-ionic solutes including polyethylene glycols having Stokes radii ≤ 0.6 nm showed considerable permeation through the apoplastic barrier in the PE envelope as indicated by greater seed thickness/breadth ratios. Permeances of dyes across the PE envelope were in the order: 2,6-dichlorophenolindophenol (DCPIP) > 2,3,5-triphenyltetrazolium chloride (TTC) ~ methyl orange ~ methylene blue > Eosin Y » Janus green ~ crystal violet ~ Evans Blue. Permeation time0.5 for DCPIP and TTC was 9.71 and 9.96 h, respectively. Dyes having Stokes radii < 0.5 nm showed significant inward as well as outward diffusion across the PE envelope in contrast to restricted diffusion of dyes having Stokes radii > 0.5 nm. Size exclusion limit for apoplastic barrier in cucumber PE envelope was resolved to be about 0.5 nm by dye permeation and around 0.8 nm by osmotic studies. Dye permeances depended primarily on particle size as described by a quadratic polynomial function rather than on charge or log D.
AB - An apoplastic barrier consisting of callose and lipid layers in the perisperm-endosperm (PE) envelope is known to restrict inward and outward transport of solutes in cucurbit seeds. The present work examines permeability properties of the barrier using cucumber seed as a model system. Osmometrically determined osmotic potential of the apoplastic fluid was used as a basis for osmotic studies aimed at examining solute exclusion from the apoplastic barrier in the PE envelope. The assessment of apoplastic permeability involved measuring the amount of anionic and cationic organic dyes diffused into agarose gel discs through the PE envelope. Ionic/non-ionic solutes including polyethylene glycols having Stokes radii ≤ 0.6 nm showed considerable permeation through the apoplastic barrier in the PE envelope as indicated by greater seed thickness/breadth ratios. Permeances of dyes across the PE envelope were in the order: 2,6-dichlorophenolindophenol (DCPIP) > 2,3,5-triphenyltetrazolium chloride (TTC) ~ methyl orange ~ methylene blue > Eosin Y » Janus green ~ crystal violet ~ Evans Blue. Permeation time0.5 for DCPIP and TTC was 9.71 and 9.96 h, respectively. Dyes having Stokes radii < 0.5 nm showed significant inward as well as outward diffusion across the PE envelope in contrast to restricted diffusion of dyes having Stokes radii > 0.5 nm. Size exclusion limit for apoplastic barrier in cucumber PE envelope was resolved to be about 0.5 nm by dye permeation and around 0.8 nm by osmotic studies. Dye permeances depended primarily on particle size as described by a quadratic polynomial function rather than on charge or log D.
KW - Apoplastic permeability barrier
KW - Callose
KW - Dyes
KW - Perisperm-endosperm (PE) envelope
KW - Size exclusion limit
KW - Stokes radius
UR - http://www.scopus.com/inward/record.url?scp=77952541025&partnerID=8YFLogxK
U2 - 10.1007/s00425-010-1146-5
DO - 10.1007/s00425-010-1146-5
M3 - Article
C2 - 20358224
AN - SCOPUS:77952541025
SN - 0032-0935
VL - 231
SP - 1483
EP - 1494
JO - Planta
JF - Planta
IS - 6
ER -