Tree responses to altered water availability range from immediate (e.g. stomatal regulation) to delayed (e.g. crown size adjustment). The interplay of the different response times and processes, and their effects on long-term whole-tree performance, however, is hardly understood.Here we investigated legacy effects on structures and functions of mature Scots pine in a dry inner-Alpine Swiss valley after stopping an 11-yr lasting irrigation treatment. Measured ecophysiological time series were analysed and interpreted with a system-analytic tree model.We found that the irrigation stop led to a cascade of downregulations of physiological and morphological processes with different response times. Biophysical processes responded within days, whereas needle and shoot lengths, crown transparency, and radial stem growth reached control levels after up to 4 yr only. Modelling suggested that organ and carbon reserve turnover rates play a key role for a tree's responsiveness to environmental changes. Needle turnover rate was found to be most important to accurately model stem growth dynamics.We conclude that leaf area and its adjustment time to new conditions is the main determinant for radial stem growth of pine trees as the transpiring area needs to be supported by a proportional amount of sapwood, despite the growth-inhibiting environmental conditions.

This article is made publicly available in the institutional repository of Wageningen University and Research, under the terms of article 25fa of the Dutch Copyright Act, also known as the Amendment Taverne. This has been done with explicit consent by the author.Article 25fa states that the author of a short scientific work funded either wholly or partially by Dutch public funds is entitled to make that work publicly available for no consideration following a reasonable period of time after the work was first published, provided that clear reference is made to the source of the first publication of the work.This publication is distributed under The Association of Universities in the Netherlands (VSNU) 'Article 25fa implementation' project. In this project research outputs of researchers employed by Dutch Universities that comply with the legal requirements of Article 25fa of the Dutch Copyright Act are distributed online and free of cost or other barriers in institutional repositories. Research outputs are distributed six months after their first online publication in the original published version and with proper attribution to the source of the original publication.

Objectives Institutionalized older adults have a high prevalence of frailty and disability, which may make them more vulnerable to the negative consequences of COVID-19. We investigated the impact of COVID-19 on the level of frailty, physical and cognitive performance in nursing home residents. Design Nested case-control study. Setting and participants. The study included nursing home residents who were infected with COVID-19 ( case group , n=76), matched by age to a control group (n=76). Methods Participants’ sociodemographic and medical data were collected, and they were also assessed for physical function (handgrip and walking speed), cognitive performance (Mini-Mental State Examination [MMSE]) and frailty (Frail-NH scale) before the first wave of the COVID-19 pandemic (October to December 2019, "pre-COVID-19") and after (June to July 2020, "post-COVID-19"). COVID-19 symptoms and clinical course were recorded for the cases . Results Between the pre- and post-COVID-19 assessments, we found a 19% greater deterioration in handgrip, a 22% greater increase in walking speed, and a 21% greater increase in Frail-NH scores in cases compared with controls. In both cases and controls, on the other hand, there was a significant 10% decrease in MMSE scores over the study period. Multivariable logistic regression showed that COVID-19 survivors had a four-fold increased chance of developing frailty compared with controls (OR = 4.95, 95% CI: 1.13-21.6, p =0.03), but not cognitive decline. Conclusions and implications COVID-19 can accelerate the aging process of institutionalized older adults in terms of physical performance and frailty by around 20%. However, we found similar levels of decline in cognitive performance in both cases and controls, likely due to the burden of social isolation and containment measures on neuropsychological health.

Across land plants there is a general pattern of xylem conduit diameters widening towards the stem base thus reducing the accumulation of hydraulic resistance as plants grow taller.In conifers, xylem conduits consist of cells with closed end-walls and water must flow through bordered pits imbedded in the side walls. As a consequence both cell size, which determines the numbers of walls that the conductive stream of water must cross, as well as the characteristics of the pits themselves, crucially affect total hydraulic resistance. Because both conduit size and pit features influence hydraulic resistance in tandem, we hypothesized that features of both should vary predictably with one another. To test this prediction we sampled a single tall (94.8 m) Sequoiadendron giganteum tree (giant sequoia), collecting wood samples from the most recent annual ring progressively downwards from the tree top to the base. We measured tracheid diameter and length, number of pits per tracheid, and the areas of pit apertures, tori, and margos. Tracheid diameter widened from treetop to base following a power law with an exponent (tracheid diameterstem length slope) of approximately 0.20. A similar scaling exponent was found between tracheid length and distance from tree top. Additionally, pit aperture, torus, and margo areas all increased (again with a power of ~0.20) with distance from tree top, paralleling the observed variation in tracheid diameter and length. Pit density scaled isometrically with tracheid length. Within individual tracheids, total permeable area of pits, measured as the sum of the margo areas, scaled isometrically with lumen area. Given that pores of the margo membrane are believed to increase in parallel with membrane area, from a strictly anatomical perspective, our results support the interpretation that pit resistance remains a relatively constant fraction of total resistance along the hydraulic pathway.