Salt stress is the prevailing threat to crop reduction worldwide especially in arid and semiarid regions since saline water is increasingly used for irrigation. Fruit thinning is a common practice in modern agriculture to manipulate sink–source interaction since fruit is the major sink organ. Moreover, containers are widely used in greenhouse crop cultivation but little attention is paid to the possible root restriction effects. Plant root systems are essential for the adaptation against different types of biotic and abiotic stresses. However, there are few studies that have been carried out on root architectural plasticity under combined stresses mentioned above due to the difficulty to access roots.
In this study, integrated root phenotyping methods were applied to study root development of tomato plants grown with various container sizes, fruit load intensities, and salinity levels. Results revealed that these combined stresses induce altered root-to-shoot ratio, root distribution, as well as biomass partitioning in different crop organs. Restricted root volume is the major factor inhibiting both physiological and morphological performance of plants. Smaller containers overexpress effects of salt stress on plants compared with what is expected in large containers. In conclusion, properly increasing container size is suggested in order to alleviate yield reduction under saline irrigation. In addition, the size of containers needs to be taken into consideration when conducting plant salt stress experiments.