Salt stress affects xylem differentiation of grey poplar (Populus × canescens)

Abstract

In this study the impact of salt stress on the physiology and wood structure of the salt-sensitive Populus x canescens was investigated. Two weeks of salt stress altered wood anatomy significantly. The xylem differentiation zone was reduced and the resulting vessels exhibited reduced lumina. To understand this phenomenon, ion composition, levels of corresponding transcripts and of the stress hormone ABA were analysed. With increasing sodium and chloride concentrations, a general reduction of potassium was found in roots and shoots, but not in leaves. Consequently, the corresponding K+ channel transcripts in roots favoured K+ release. The overall osmolarity in leaves was up to fourfold higher than in roots or shoots. Therefore, adjustment of the K+/Na+ balance seemed not to be required in leaves. Sodium increased gradually from roots to shoots and then to leaves indicating that sodium storage took place first in roots, then in shoots, and finally in leaves to protect photosynthesis from salt effects as long as possible. Since leaf abscisic acid levels markedly increased, stomatal closure seemed to limit CO2 uptake. As a consequence, diminished nutrient supply to the cambium in combination with lowered shoot K+ content led to decreased vessel lumina, and a reduction of the radial cambium was observed. Thus, xylem differentiation was curtailed and the development of full size vessels was impaired.

Alterações anatômicas em folhas e raízes de Jatropha curcas L. cultivadas sob estresse salino

“…3F). Comportamento similar foi observado em raízes de Populus x canescens nas quais ocorreu uma redução das camadas e do diâmetro dos elementos de vasos, à medida que aumentava o período de exposição a solos salinizados (ESCALANTE-PÉREZ et al, 2009;JUNGHANS et al, 2006). Verificou-se, também, que o incremento da concentração salina resultou em maior lignificação G. M. Melo et al das células xilemáticas e endodérmicas (FIG.…”

TheArabidopsisNAC Transcription Factor VNI2 Integrates Abscisic Acid Signals into Leaf Senescence via theCOR/RDGenes

“…Especially, differentiation of xylogenic cambium is a flexible developmental process that is also influenced by environmental factors (Junghans et al, 2006). Indeed, xylem differentiation zone and lumina are reduced under high salt conditions (Escalante-Pé rez et al, 2009). It is therefore likely that VNI2 transcriptional repressor activity during xylem vessel development would be compromised by the transcription activation domain that is active under high salt conditions, contributing to plant fitness for enhanced stress tolerance and leaf longevity.…”

The Hydraulic Architecture of Populus

“…Salt-stressed plants developed fewer radial cell layers in the cambial zone and narrower vessels than control trees (Escalante-Pérez et al 2009 ). Junghans et al ( 2006 ) reported that high salt concentrations reduced cambial activity and vessel diameters of P. × canescens plants.…”

“…The wider vessel diameters of nonstressed P. × canescens plants may be associated with higher indole-3-acetic acid (IAA) concentrations in the xylem of control plants (Junghans et al 2006 ). Salinity may also cause increased ABA synthesis and accumulation, which in turn may modulate various physiological processes related to plant hydraulics (Escalante-Pérez et al 2009 ;Shatil-Cohen et al 2011 ).…”