A Sizer model for cell differentiation in Arabidopsis thaliana root growth

Plant roots grow due to cell division in the meristem and subsequent cell elongation and differentiation, a tightly coordinated process that ensures growth and adaptation to the changing environment. How the newly formed cells decide to stop elongating becoming fully differentiated is not yet understood. To address this question, we established a novel approach that combines the quantitative phenotypic variability of wild-type Arabidopsis roots with computational data from mathematical models. Our analyses reveal that primary root growth is consistent with a Sizer mechanism, in which cells sense their length and stop elongating when reaching a threshold value. The local expression of brassinosteroid receptors only in the meristem is sufficient to set this value. Analysis of roots insensitive to signaling and of roots with gibberellin biosynthesis inhibited suggests distinct roles of these hormones on cell expansion termination. Overall, our study underscores the value of using computational modeling together with quantitative data to understand root growth

Policy-driven monitoring and evaluation : Does it support adaptive management of socio-ecological systems?

Inadequate Monitoring and Evaluation (M&E) is often thought to hinder adaptive management of socio-ecological systems. A key influence on environmental management practices are environmental policies: however, their consequences for M&E practices have not been well-examined. We examine three policy areas - the Water Framework Directive, the Natura 2000 Directives, and the Agri-Environment Schemes of the Common Agricultural Policy - whose statutory requirements influence how the environment is managed and monitored across Europe. We use a comparative approach to examine what is monitored, how monitoring is carried out, and how results are used to update management, based on publicly available documentation across nine regional and national cases. The requirements and guidelines of these policies have provided significant impetus for monitoring: however, we find this policy-driven M&E usually does not match the ideals of what is needed to inform adaptive management. There is a tendency to focus on understanding state and trends rather than tracking the effect of interventions; a focus on specific biotic and abiotic indicators at the expense of understanding system functions and processes, especially social components; and limited attention to how context affects systems, though this is sometimes considered via secondary data. The resulting data are sometimes publicly-accessible, but it is rarely clear if and how these influence decisions at any level, whether this be in the original policy itself or at the level of measures such as site management plans. Adjustments to policy-driven M&E could better enable learning for adaptive management, by reconsidering what supports a balanced understanding of socio-ecological systems and decision-making. Useful strategies include making more use of secondary data, and more transparency in data-sharing and decision-making. Several countries and policy areas already offer useful examples. Such changes are essential given the influence of policy, and the urgency of enabling adaptive management to safeguard socio-ecological systems. Highlights • Policy strongly influences Monitoring & Evaluation (M&E) of socio-ecological systems. • We examine M&E of 3 major European policies in 9 regional and national cases. • Policy-driven M&E is imperfect versus ideals of M&E to support adaptive management. • Attention needed to systems, social issues, sharing data, and sharing intended uses. • Examples from across Europe and different policies offer ideas for improvement

Frontier Analysis

This article presents a comprehensive review of frontier studies in the tourism literature. We discuss the main advantages and disadvantages of the various frontier approaches, in particular, the nonparametric and parametric frontier approaches. The study further differentiates between micro and macro applications of these approaches, summarizing and critically reviewing the characteristics of the existing studies. We also conduct a meta-analysis to create an overview of the efficiency results of frontier applications. This allows for an investigation of the impact of frontier methodology on tourism research. The present review also highlights the limitations of existing studies and suggests an agenda for future research