Main content area

Light spectral and thermal properties govern biomass allocation in tomato through morphological and physiological changes

Kim, Hye-Ji, Lin, Meng-Yang, Mitchell, Cary A.
Environmental and experimental botany 2019 v.157 pp. 228-240
Solanum lycopersicum, biomass, canopy, chlorophyll, chronic exposure, dry matter partitioning, flowering, fruit yield, fruits, greenhouses, heat, lamps, leaf area, leaves, light emitting diodes, photons, photoperiod, photosynthesis, photosynthetically active radiation, plant growth, red light, roots, temperature, thermal properties, tissues, tomatoes, transpiration, water content
We investigated the effects of light spectral and thermal properties on biomass allocation among vegetative and reproductive structures in tomato (Solanum lycopersicum L. ‘Merlice’) plants during growth and development and to determine its underlying mechanisms. Plants were grown in a greenhouse under a DLI of 3.4 mol m2 day−1 with/without supplemental lighting and a 16-h photoperiod, provided at equal photosynthetic photon flux density (PPFD of 230 μmol m‒2 s‒1 either from overhead high-pressure sodium (HPS) lamps or intracanopy light-emitting diode (LED) arrays: red light alone (R100; 100% of photosynthetically active radiation (%PAR)), red plus low far-red (R100+FR21), red plus high far-red (R100+FR41), and red plus blue (R61+B39). Supplemental lighting substantially increased total biomass and fruit yield, but to a greater extent by LED lighting regardless of spectrum. However, spectral contribution to leaf morphological traits and biomass allocation pattern varied greatly among the light treatments. HPS-supplemented plants had higher leaf temperature, photosynthetic rate (Pn), and transpiration rate (E) in the upper foliar canopy (161 to 240 cm from the base of the shoot) and contained higher water content in all tissues, particularly in roots by 2-fold, compared to LED-supplemented plants. They also had thinner, smaller leaves and allocated a higher fraction of total biomass to vegetative tissues, demonstrating their allocation strategies for effective transpiration and heat dissipation. Meanwhile, LED-supplemented plants allocated biomass preferentially to reproductive structures at the expense of vegetative tissues. Inclusion of higher FR or B with R light decreased leaf biomass fraction relative to total biomass but increased leaf dry mass and leaf thickness. Particularly, supplemental FR light significantly lowered the water content of leaves and fruits compared to B light. Long-term exposure of tomato plants to low R:FR was associated with reductions in leaf area, chlorophyll content, and vegetative shoot biomass fraction, increases in leaf thickness and fruit biomass, and acceleration of flowering and fruiting. Light-induced biomass allocation changed between vegetative and reproductive structures during plant growth and development. FR light had the most pronounced effect in this regard by significantly shifting dry-mass accumulation to fruits, via more efficient photosynthetic mechanisms and conserved water use. We conclude that light spectral and thermal properties affect biomass allocation among plant parts during tomato growth and development, and such responses involve morphological and physiological changes in tomato plants, ultimately affecting crop performance and yield.