Can gene regulatory networks be used for predicting the response of leaf growth to water deficit?
In each of the above-mentioned mechanisms, widely believed to be involved in the response of leaf growth to water deficit, there still are fundamental debates on the effects of the considered functions or genes. Instead of simplifying the picture, the molecular dissection of each mechanism has tended to increase its complexity, to generate new debates and increase the number of involved genes because several families of up to 30 genes are involved in each single mechanism. Transcriptome analyses should help to analyse this complexity but provide no avenues for modelling plant behaviour. Another difficulty concerns the phenotypic analysis. When plant survival is analysed, the phenotype is qualitative with two possibilities (alive / dead), as in the gene regulatory network analysed by Gilman and Arkin (2002). When leaf growth is analysed, the phenotype is quantitative i.e. an infinite number of values of each variable and of combinations of variables are possible. The analysis of plant p
