Distribution of indole-3-acetic acid in Petunia hybrida shoot tip cuttings and relationship between auxin transport, carbohydrate metabolism and adventitious root formation

Abstract

To determine the contribution of polar auxin transport (PAT) to auxin accumulation and to adventitious root (AR) formation in the stem base of Petuniahybrida shoot tip cuttings, the level of indole-3-acetic acid (IAA) was monitored in non-treated cuttings and cuttings treated with the auxin transport blocker naphthylphthalamic acid (NPA) and was complemented with precise anatomical studies. The temporal course of carbohydrates, amino acids and activities of controlling enzymes was also investigated. Analysis of initial spatial IAA distribution in the cuttings revealed that approximately 40 and 10 % of the total IAA pool was present in the leaves and the stem base as rooting zone, respectively. A negative correlation existed between leaf size and IAA concentration. After excision of cuttings, IAA showed an early increase in the stem base with two peaks at 2 and 24 h post excision and, thereafter, a decline to low levels. This was mirrored by the expression pattern of the auxin-responsive GH3 gene. NPA treatment completely suppressed the 24-h peak of IAA and severely inhibited root formation. It also reduced activities of cell wall and vacuolar invertases in the early phase of AR formation and inhibited the rise of activities of glucose-6-phosphate dehydrogenase and phosphofructokinase during later stages. We propose a model in which spontaneous AR formation in Petunia cuttings is dependent on PAT and on the resulting 24-h peak of IAA in the rooting zone, where it induces early cellular events and also stimulates sink establishment. Subsequent root development stimulates glycolysis and the pentose phosphate pathway.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-013-1907-z) contains supplementary material, which is available to authorized users.

WOX11 and 12 Are Involved in the First-Step Cell Fate Transition during de Novo Root Organogenesis in Arabidopsis

“…Among many different cell types in the leaf explant, procambium cells, probably also including some other parenchyma cells surrounding the procambium, are likely to serve as competent cells that initiate adventitious roots and callus. This is not only supported by several previous studies (Greenwood et al, 2001;Ahkami et al, 2009Ahkami et al, , 2013Yu et al, 2010;Correa Lda et al, 2012;de Almeida et al, 2012), but also supported by the specific WOX11 expression patterns upon auxin induction. It was proposed that callus is initiated from the pericycle-like cells surrounding the vascular tissues when aerial organs are used as explants, but the nature of the pericycle-like cells was unknown (Sugimoto et al, 2010(Sugimoto et al, , 2011.…”

“…Several previous histological observations revealed that both adventitious roots and shoots initiate from the procambium or cambium (Greenwood et al, 2001;Ahkami et al, 2009Ahkami et al, , 2013de Almeida et al, 2012;Correa Lda et al, 2012), and callus also initiates from procambium cells (Yu et al, 2010). Thus, it is possible that procambium cells, perhaps together with some parenchyma cells near the procambium in leaf explants, function like the xylempole pericycle cells in roots to produce callus, adventitious roots, and adventitious shoots.…”

Mini-grafting of adult Passiflora edulis Sims f. flavicarpa Deg. scions onto vegetatively propagated adult rootstocks of P. mucronata Lam.

“…Apical meristems and young leave have high concentrations of free auxins since they are the main locations of biosynthesis of this phytohormone (Taiz and Zeiger, 2013). Ahkami et al (2013), analyzed the spatial distribution of IAA (indole-acetic acid) in Petunia hybrida stem and verified higher concentrations in young leaves close to the stem, but the levels decreased furthest from the apical region. This suggests that the length of shoots on the cuttings is beneficial for grafting.…”

PENGGUNAAN MEDIA, BAHAN STEK, DAN ZAT PENGATUR TUMBUH TERHADAP KEBERHASILAN STEK MASOYI (Cryptocarya massoy (Oken) Kosterm)

“…Perpanjangan sel yang terjadi pada stek masoyi diduga dipengaruhi oleh hormon endogen dan ketersediaan air. Ahkami et al (2013) menyebutkan ketersediaan air mampu menyebabkan pengenduran dinding sel sehingga mampu mendesak pembesaran sel dan pembentukan pembentukan akar .…”