Influence of light and sucrose on leaf initiation rate of young tomato plants.

MSc-thesis abstract (submitted 19 April 2015):
Leaf formation is an essential process in plants; the speed of this process is tightly regulated in response to the prevailing environmental conditions. Temperature is the main factor influencing plant development and leaf initiation rate (LIR). Additionally, plants can also regulate their LIR in response to light.

The involvement of photoreceptor, hormone and sugar signalling in a complex LIR regulation web is gaining strength and support by numerous research works. Notwithstanding, there is still a great knowledge gap in the understanding of leaf initiation process regulation by light. In this experimental work we utilized in-vitro culture systems with detached shoot apices and intact seedlings. Light intensity and media sucrose concentration were utilized as treatments in order to evaluate LIR responses; apical buds were analysed for carbohydrate content and sucrose metabolization via three sucrose cleavage enzymes (cell wall invertase, CWINV; vacuolar invertase, VINV; sucrose synthase, SUS). Light intensities below photosynthesis compensation point were enough to trigger sugar transport and metabolization together with growth responses characteristic of high light intensity grown plants. Our results point out to a combination of sugar status, light signals and localized glucose signaling mediated by invertases to regulate LIR of plants.