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Functional–structural plant models (FSPMs) explore and integrate relationships between a plant’s structure and processes that underlie its growth and development. In recent years, the range of topics being addressed by scientists interested in functional–structural plant modelling has expanded greatly. FSPM techniques are now being used to dynamically simulate growth and development occurring at the microscopic scale involving cell division in plant meristems to the macroscopic scales of whole plants and plant communities. The plant types studied also cover a broad spectrum from algae to trees. FSPM is highly interdisciplinary and involves scientists with backgrounds in plant physiology, plant anatomy, plant morphology, mathematics, computer science, cellular biology, ecology and agronomy. This special issue of Annals of Botany features selected papers that provide examples of comprehensive functional–structural models, models of key processes such as partitioning of resources, software for modelling plants and plant environments, data acquisition and processing techniques and applications of functional–structural plant models for agronomic purposes.

Lolium perenne (L.) is one of the most important species in temperate grasslands. Temperature is a major factor controlling plant development. Breeding L. perenne cultivars adapted to new ranges of temperature could be necessary under most climate change scenarios. However, before any breeding effort in such direction, knowing the intraspecific variability of responses to temperature is essential. Our objective was to analyze a sample of accessions of L. perenne for their response to constant temperature during germination and initial heterotrophic growth. Eight accessions were taken out from a genebank containing 160 accessions. Six accessions were wild populations collected in different places in France and the other two were populations from a selection program. For germination, four replicates of 100 seeds per accession were tested in Petri dishes in the dark at eight constant temperatures, from 5 to 40°C with increases of 5°C. Germination countings were carried out at variable time intervals and durations that depended on treatments. For initial heterotrophic growth analysis, seeds were germinated at 25°C. Sets of 30 seedlings per accession were placed in polypropylene boxes on blotter blue paper and transferred to each one of the eight treatments in the dark. They were pictured at variable time intervals for root and shoot growth measurement by image analysis. Neither seed germination nor heterotrophic growth was observed at 40°C, for any accession. Temperature and time course response surfaces were markedly different between accessions. Equally, maximum germinability and the shape of the response curves to temperature were significantly different between accessions. This means that limited similarities between responses were observed. Furthermore, germination rates followed the non-linear beta function with significant differences between some accessions. These also showed significant differences in their root and shoot growth rate in response to temperature. In general, the relative growth rates of roots and shoots were slow at 5°C, peaked between 25 and 30°C, and showed a sharp reduction afterward. These results reveal, for the first time, high genetic variability within L. perenne germplasm for the response to temperature in the initial life phases. This discovered variability should serve breeders to create perennial ryegrass varieties for the future. [ABSTRACT FROM AUTHOR]

Quantifying and simulating the relationships between crop growth, total‐nitrogen (total‐N) and nitrate‐N (NO3–‐N) concentration can improve crop nutritional husbandry. In this study, the relationship between shoot relative growth rate (RGR) and shoot total‐N, organic‐N and NO3–‐N concentration of hydroponically‐grown lettuce (Lactuca sativa var. capitata L. cv. Kennedy) was described and simulated. Plants were grown hydroponically for up to 74 d. Nitrogen was supplied throughout (control; T1), or removed at 35 d (T2) and 54 d (T3), respectively, after sowing. The organic‐N and NO3–‐N concentration declined in the shoots of control plants with growth, until commercial maturity approached when organic‐N and NO3–‐N concentration increased. There were sub‐linear relationships between both total‐N and organic‐N concen tration, and shoot RGR, in the N‐limited treatments, i.e. shoot RGR approached an asymptote at high shoot N concentration. The proportional effects of total‐N and organic‐N concentration on shoot RGR were independent of plant age. A dynamic simulation model (‘Nicolet’), derived previously under different conditions, was used to simulate the growth, dry matter content, organic‐N, and NO3–‐N concentration of lettuce grown under the extreme N‐stress conditions experienced by the plants. In view of the largely successful fitting of the model to experimental data, the model was used to interpret the results. Suggestions for model improvement are made. [ABSTRACT FROM PUBLISHER]

Developmental responses to temperature are critical to yield formation in crops and perennial grassland species. However, their characterisation over a broad range of temperatures relevant to climate change studies has been limited in these species. The present study sought to determine the non-linear developmental responses to temperature of two major grassland species, tall fescue ( Festuca arundinacea ) and alfalfa ( Medicago sativa ), and to assess i) whether a coordinated response occurred between different developmental processes, ii) if genotypes from contrasting origins differed in their responses, and iii) to quantify how a lack of coordination and genetic variability might affect estimates of thermal time progression under present and future climate scenarios. Two series of experiments were carried out under controlled conditions with eight constant temperatures ranging from 5 °C to 40 °C applied to seedlings and mature plants. Different growth and developmental processes were characterized, including shoot development and radicle, leaf and stem growth. Once normalized to a temperature of 20 °C, the temperature responses of the different processes displayed no significant variability between temperate and Mediterranean genotypes. On the other hand, not all developmental processes within a genotype displayed a coordinated response to temperature. Significant departures from the response of shoot development in mature plants were observed regarding several processes, particularly at low and supra-optimal temperatures (up to ±5 °C and ±2 °C for minimal and maximal temperature estimates, respectively). Differences were particularly marked relative to node and stem elongation responses. Overall, when using the temperature dependencies of different processes to estimate cumulative thermal time, significant bias was observed in alfalfa when considering stem elongation by comparison with other processes. The consequences for improvements to forage crop models, and for the meta-analyses often used to calibrate them, are discussed. [ABSTRACT FROM AUTHOR]