Soil Compaction. A Role for Ethylene in Regulating Leaf Expansion and Shoot Growth in Tomato?

Abstract

The role of ethylene in regulating growth in tomato (Lycopersicon esculentum Mill.) during compaction stress was examined using wild-type (cv Ailsa Craig) and transgenic (ACO1 AS ) genotypes; the latter has a reduced capacity to produce ethylene. Ethephon or silver ions were applied to increase ethylene production or block its action. Shoot growth in both genotypes was comparable in uncompacted (1.1 g cm ؊3 ) and uniformly compacted soil (1.5 g cm ؊3 ). However, a 1.1/1.5-g cm ؊3 split-pot treatment invoked marked genotypic differences: growth was reduced in cv Ailsa Craig but was comparable to uncompacted control plants in ACO1 AS . As xylem sap abscisic acid levels were similar, abscisic acid was not responsible for inhibiting growth in cv Ailsa Craig. These genotypic differences in growth were accompanied by increased ethylene evolution in cv Ailsa Craig, suggesting that the ability of ACO1 AS to maintain growth in the split-pot treatment reflected its lower ethylene levels, a view supported by the observation that excising the roots in the compacted compartment reduced ethylene evolution and restored shoot growth in cv Ailsa Craig. Treatment with silver restored shoot growth in cv Ailsa Craig, whereas treatment with ethephon reduced growth in ACO1 AS . Thus, ethylene apparently has a key role in determining growth when tomato plants encounter differential soil compaction.Plants grown in compacted soil frequently exhibit reductions in root and shoot growth and stomatal conductance in the absence of significant effects on foliar water status

Interaction with ethylene: changing views on the role of abscisic acid in root and shoot growth responses to water stress

“…6; Saab et al 1990Saab et al , 1992 remains the only demonstration of enhanced shoot growth in response to endogenous ABA deficiency at low water potentials. The apparent change in response to ethylene during shoot development in those experiments, from promotive to inhibitory, is consistent with reports that ethylene stimulates mesocotyl growth in some species (Suge 1971;Cornforth & Stevens 1973), whereas it is usually inhibitory to shoot growth of terrestrial plants at later stages of development (Abeles, Morgan & Saltveit 1992;Lee & Reid 1997;Hussain et al 1999). The following sections summarize recent studies which suggest that restriction of ethylene production may be a common function of ABA and therefore that endogenous ABA may often act to maintain rather than inhibit shoot growth.…”

“…Leaf growth of plants growing in compacted soil was more inhibited in Az34 than in the wild type, and the evidence suggested that changes in leaf water relations were not the cause. Recent studies from the same group demonstrated that ethylene was a major cause of the inhibition of shoot growth in tomato plants grown with their root system divided between pots of uncompacted and compacted soil (Hussain et al 1999(Hussain et al , 2000. As shown in Fig.…”

Stomatal Responses in Rainfed Lowland Rice to Partial Soil Drying; Comparison of Two Lines

“…The greater inherent ability of CT9993 to elongate roots at depth was also reported by Azhiri-Sigari et al (2000), and was consistent with field studies (Samson et al, 2002), and other wax-layer experiments (Babu et al, The similar Ψ L and g s of the plants grown under both soft and hard wax layers under all water regimes with or without root severing implied a negligible effect of impedance on root signals in this study (Fig. 4a, b, c), which differs from other reports (Mulholland et al, 1996;Hussain et al, 1999;Roberts et al, 2002). The reason for this discrepancy could be attributed to the numbers of roots escaping between the wax layer and the wall of the cylinder.…”

“…In response to hardpans or compacted soils, Hartung et al (1994), Mulholland et al (1996Mulholland et al ( , 1999, Hussain et al (1999) and Roberts et al (2002) showed that increased ABA export from roots encountering compacted soil was responsible for the concurrent reductions in stomatal conductance in various crops. However, Ismail et al (1994) found no evidence for the involvement of ABA as a root signal in mediating responses to restricted root growth in cowpea.…”

Avaliação de modelo de extração da água do solo por sistemas radiculares divididos entre camadas de solo com propriedades hidráulicas distintas

“…Uma forma experimental de impor essas condições é pela utilização de um lisímetro dividido (split-pot): um recipiente especial em que o sistema radicular de uma planta é dividido em duas partes, separadas fisicamente e monitoradas. Método semelhante foi empregado por Lascano & van Bavel (1986), Kosola & Eissenstat (1994), Hussain et al (1999) A superfície do solo foi coberta com plástico e uma camada de aproximadamente 2 cm de areia grossa, com o objetivo de minimizar a perda de água por evaporação nos lisímetros. As plantas foram irrigadas manualmente, mantendo-se um teor de água adequado para seu desenvolvimento com um potencial matricial em torno de -2 m, até atingirem o estádio reprodutivo.…”