Effects of long-term high light on tomato : a physiological, cellular, and molecular study

Abstract

Light is a vital regulator that controls physiological and cellular responses to modulate plant growth, development, yield, and quality. Plant growth, morphogenesis, and other physiological responses of plants are affected by the intensity and quality of light. Refined sensing and response to the intensity, direction, duration, and wavelength of light are essential to plants. Light is a primary energy source for photosynthesis and a vital regulator of mineral nutrient uptake and distribution in plants. Tomato is a photophilous crop that largely depends on higher light intensity for improved growth, development, and accumulation of metabolites. High light (HL) with supplementary lighting is expected to improve yield and fruit quality in the greenhouse (GH), but long-term high light usually leads to reduced plant growth and photo-oxidative damage to cell function. Therefore, it is important to study the influence of high light intensity on leaf function and fruit quality, as well as the coordination of light signalling from the leaf to the fruit. This thesis generated comprehensive knowledge of light-induced morphological, physiological, and molecular changes in the leaf and fruit. I undertook long-term high light effects on the morphological, physiological, cellular, and molecular responses of the tomato plant including leaf and fruit to decipher light signalling transduction in plants with transcriptional regulation from the leaf to the fruit. In summary, light-induced differential photosynthetic performance and ion fluxes in leaves may implicate a requirement for more uniform light irradiance and spectra at different canopy-level of tall greenhouse tomato plants. However, this indirect link to the interactive regulation of tomato fruit quality with light signalling in tomato leaves is yet to be validated through molecular analyses for the early prediction of yield and postharvest quality of tomatoes in protected horticultural production. Nevertheless, the different signals transduced from leaf to fruit during signalling cascades are thought to be interlinked, their coordination and hierarchy still need to be determined and complemented in the direct leaf and fruit quality experiments with cross-talks. Therefore, optimisation of the right light combination that can boost both tomato production and fruit quality in the greenhouse is worth scrutinising in long-term high light.

Date of Award	2022
Original language	English