The majority of experiments in plant biology use plants grown in some kind of container or pot. We conducted a meta-analysis on 65 studies that analysed the effect of pot size on growth and underlying variables. On average, a doubling of the pot size increased biomass production by 43%. Further analysis of pot size effects on the underlying components of growth suggests that reduced growth in smaller pots is caused mainly by a reduction in photosynthesis per unit leaf area, rather than by changes in leaf morphology or biomass allocation. The appropriate pot size will logically depend on the size of the plants growing in them. Based on various lines of evidence we suggest that an appropriate pot size is one in which the plant biomass does not exceed 1 g L–1. In current research practice ~65% of the experiments exceed that threshold. We suggest that researchers need to carefully consider the pot size in their experiments, as small pots may change experimental results and defy the purpose of the experiment.

Seedlings of four populations each of Pinus pinaster, P. halepensis, P. canariensis and P. pinea were grown in controlled conditions to evaluate both inter- and intra-specific differences in response to watering. We submitted half of the plants to a moderate water stress and after 22 weeks, we recorded height, stem diameter and root, stem and leaves dry weight. Patterns and amounts of phenotypic changes, including changes in biomass allocation, were analysed. We found a scant response in P. canariensis, P. pinaster and P. halepensis presented high population divergence for phenotypic changes, and P. pinea showed marked allocational shifts and no population divergence. The phenotypic changes observed within species are interpreted as a plastic response. The variation encountered within P. halepensis and P. pinaster may be indicative of specialisation to either resource-rich or resource-poor habitats, being populations from favourable sites more plastic. P. pinea exhibited a very uniform plastic response, indicating generalist behaviour.

A plastic response towards enhanced reproduction is expected in stressful environments, but it is assumed to trade off against vegetative growth and efficiency in the use of available resources deployed in reproduction [reproductive efficiency (RE)]. Evidence supporting this expectation is scarce for plants, particularly for long‐lived species. Forest trees such as Mediterranean pines provide ideal models to study the adaptive value of allocation to reproduction vs. vegetative growth given their among‐population differentiation for adaptive traits and their remarkable capacity to cope with dry and low‐fertility environments. We studied 52 range‐widePinus halepensispopulations planted into two environmentally contrasting sites during their initial reproductive stage. We investigated the effect of site, population and their interaction on vegetative growth, threshold size for female reproduction, reproductive–vegetative size relationships andRE. We quantified correlations among traits and environmental variables to identify allocation trade‐offs and ecotypic trends. Genetic variation for plasticity was high for vegetative growth, whereas it was nonsignificant for reproduction. Size‐corrected reproduction was enhanced in the more stressful site supporting the expectation for adverse conditions to elicit plastic responses in reproductive allometry. However,REwas unrelated with early reproductive investment. Our results followed theoretical predictions and support that phenotypic plasticity for reproduction is adaptive under stressful environments. Considering expectations of increased drought in theMediterranean, we hypothesize that phenotypic plasticity together with natural selection on reproductive traits will play a relevant role in the future adaptation of forest tree species.