Towards a conceptual ABA ideotype in plant breeding for water limited environments

Abstract

A huge amount of information had been accumulated on abscisic acid (ABA). Laboratory and some field research with ABA-enhanced transgenic plants generally conclude that ABA is a drought resistance hormone, since it causes stomatal closure, reduces transpiration and results in ‘water saving’ under drought stress. This recurring conclusion is hard to accept in the agronomic domain considering the many direct and indirect negative effects of ABA on plant growth and reproduction. In order to formulate a conceptual phenotypic ABA ideotype for plant breeding, this paper begins by briefly reviewing the phenomics of ABA relative to plant function and productivity. Consequently, it is recognised that ABA enhancement is important in controlling the isohydric (‘water saving’) plant model, whereas plant hydraulics are more important in controlling the anisohydric (‘water spending’) plant model. Subsequently, the respective isohydric and anisohydric ideotypes appropriate to specific dryland crop drought stress scenarios are proposed. It is concluded that ABA can by no means be universally defined as a ‘drought resistance hormone’. Its benefit or damage depends on the crop drought stress profile and the dynamics of the seasonal regimen of ABA in the plant. The isohydric ideotype might have an advantage in the harshest environments, whereas the anisohydric one will perform relatively better under more moderate drought conditions.

Plant Responses to Salt Stress: Adaptive Mechanisms

“…When drought and heat co-occur, stomatal closure and decreased transpiration, associated with high WUEi, may lead to a dramatic increase in leaf temperature (up to 7 °C above air temperature) [154]. If this situation remains for long periods of time, leaf photodamage and/or xylem embolism may occur, leading to severe defoliation and plant death [155].…”

Root traits and their potential links to plant ideotypes to improve drought resistance in common bean

“…At root system level, their response to drought stress could differ not only between species but also within species (Lynch 2013). Drought stress also impacts the pattern of water uptake and use depending on the origin and evolution of the species and the agro-climatic conditions faced by them (Blum 2015).…”

“…According to agroecological zones and types of drought, breeding should target different plant ideotypes such as, the isohydric ('water saving') plant model and the anisohydric ('water spending') plant model (Polania et al 2016a). The water saving model might have an advantage in the harshest environments, whereas the water spending model will perform relatively better under more moderate drought conditions (Blum 2015). Effective use of water (EUW), as proposed by (Blum 2009), implies not only maximal soil moisture capture for transpiration but also decreased non-stomatal transpiration and minimal water loss by soil evaporation.…”

Involvement of aerial organs on the ABA accumulation in roots of Citrus plants under water deficit

“…This was demonstrated using reciprocal grafting of ABA et al, 2015;Blum, 2015b) sourced ABA on the stomatal closure is not conclusive since it could be interplaying with other factors that simultaneously regulate the stomatal aperture such as hydraulic signals ., Jones, 2015;Blum, 2015b) (Kudoyarova ., 2011Dodd, 2013;Stevenick, 2013) In the context of water deficit, two main factors act interfering with the suppos shoot ABA: the first relies on the ability of dehydrated leaves to increase ABA concentration in this organ. This was demonstrated using reciprocal grafting of ABA ., Blum, 2015b) sourced ABA on the stomatal closure is not conclusive since it could be interplaying with other factors that simultaneously regulate the stomatal aperture such as hydraulic signals (Soar ., 2010;Jones, 2015;Blum, 2015b) ( Kudoyarova et al, 2011; or even other phytohormones ., 2014; McAdam et al shoot model. Plant roots detected the crease in soil water potential and triggers the ABA synthesis in this organ.…”

“…This was demonstrated using reciprocal grafting of ABA Jones, 2015;Blum, 2015b) , hydraulic conductance ., 2011; Dodd, 2013;Stevenick, 2013) ., 2013; Puertolas et al Schematic representation of the root-to crease in soil water potential and triggers the ABA synthesis in this organ. ABA is transported via xylem sap to leaves inducing the stomatal closure to prevent water loss.…”