Adaptive nature of the transition phases in development: the case of Sorghum bicolor

Abstract

An increase in tolerance to salinity is induced in Sorghum bicolor by exposure to a sublethal concentration of NaCl during early vegetative development. The phase of competence for induction of this response, termed salt adaptation, is well defined in time and it coincides with the emergence of the first adventitious roots. The link between these events was investigated. Competence for salt adaptation varies among genotypes. It is shown that competence is especially high for genotypes in which the link between the seminal root and the shoot is reduced during emergence of the adventitious root. These data relate the capacity for salt adaptation with development in the absence of NaCl, suggesting that: (i) functional integration of the adventitious roots within the whole plant has an adaptive nature in normal development; (ii) salt adaptation results from an integration of the environmental constraint (NaCl) during this developmental readjustment. It is concluded that perturbations generated by emergence of a new organ are the cause of rapid variations in sensitivity required to open a competence window.

Data analysis in plant physiology: are we missing the reality?

“…This process was clearly observed during normal development (Amzallag 1999d(Amzallag , 2001b. As shown in S. bicolor, physiological adaptation to salinity (expressed exclusively during a developmental window, see Amzallag, Seligmann & Lerner 1993) is also clearly related to the decrease in organ connectance during the early vegetative critical period (Amzallag 1999d). It is likely that the adaptive properties inherent to developmental plasticity (Sultan 1995) are an expression of this phenomenon.…”

“…Although resulting from mathematical transformations, connectance reflects biological phenomena. Changes in connectance were observed during specific phases of development in Sorghum, and they were related to the adaptive phenotypic plasticity of the plant (Amzallag & Seligmann 1998;Amzallag 1999d). Connectance is also affected by hormonal treatments (CK and GA) even before any significant effect on growth (Amzallag 1999c(Amzallag , 2001a).…”

“…Developmental events (senescence or emergence of a new organ, change from vegetative to reproductive development) involves temporary drops in connectance during specific phases of development, also termed critical periods. For example, a reduced connectance has been observed during the replacement of the seminal root by the adventitious root during the early vegetative development of Sorghum (Amzallag 1999d). This drop in global connectance is the expression of a temporary decrease in influence of the whole-plant regulations on growth of an organ.…”

Individuation in Sorghum bicolor: a self‐organized process involved in physiological adaptation to salinity

“…The number of these discrete stages itself depends on the interaction between developmental and environmental constraints. In Sorghum bicolor, a linkage was previously observed between salt-adaptation and events occurring during specific transition phases in normal development (Amzallag 1999). I concluded that normal development includes adaptive events, so environment cannot be restricted to a trigger for the expression of a pre-existing genetic programme.…”

Ontogeny modifies the effects of water stress on stomatal control, leaf area duration and biomass partitioning of Pennisetum glaucum

“…Grain yield also depends on developmental processes such as meristem differentiation, meiosis or pollination, which are not directly related to the plant leaf area. In sorghum, Amzallag (1999) showed that the plant sensitivity to environmental stresses depends on the hormonal metabolism integrating the different meristems within the whole organism. This functional integration of the various meristems depends on the timing of morphogenesis, which could explain the irreparable damage on final grain production caused by environmental stress during earlier phases of development.…”