At high light intensities (summer) deeper penetration of light in the canopy improves crop photosynthesis, but not at low light intensities (winter). In particular, internode length and leaf shape affect the vertical distribution of light in the canopy. A new plant ideotype with more spacious canopy architecture due to long internodes and long and narrow leaves led to an increase in crop photosynthesis of up to 10 %.

Leaf angles of heterogeneous canopies should be explicitly described as they have a big impact both on light distribution and photosynthesis. Especially, the vertical variation of photosynthesis in canopy is such that the experimental approach of photosynthesis measurements for model parameterization should be revised.

No abstract

The model of cut-rose presented allowed the creation of a range of initial structures thanks to interactive rules for pruning, cutting and bending. These static structures can be regarded as departure points for the dynamic simulation of production of flower canes. Furthermore, the model was able to predict local (per leaf) light absorption and photosynthesis. It can be used to investigate the physiology of ornamental plants, and provide support for the decisions of growers and consultants.

Water stress in plants affects a number of physiological processes such as photosynthetic rate, stomatal conductance as well as the operating efficiency of photosystem II (PSII) and non‐photochemical quenching (NPQ). Photochemical reflectance index (PRI) is reported to be sensitive to changes in xanthophyll cycle which occur during stress and could possibly be used to monitor changes in the parameters mentioned before. Therefore, the aim of this study was to evaluate the use of PRI as an early water stress indicator. Water stress treatment was imposed in a greenhouse tomato crop. CO2 assimilation, stomatal conductance, light‐adapted and dark‐adapted fluorescence as well as PRI and relative water content (RWCs%) of the rooting medium were repeatedly measured. The same measurements were also performed on well‐irrigated plants that acted as a reference. The experiment was repeated in four consecutive weeks. Results showed a strong correlation between RWCs% and photosynthetic rate, stomatal conductance, NPQ and operating efficiency of PSII but not with PRI when the whole dataset was considered. Nevertheless, more detailed analysis revealed that PRI gave a good correlation when light levels were above 700 µmol m−2 s−1. Therefore, the use of PRI as a water stress indicator cannot be independent of the ambient light conditions.