Daily Changes in Temperature, Not the Circadian Clock, Regulate Growth Rate in Brachypodium distachyon

Abstract

Plant growth is commonly regulated by external cues such as light, temperature, water availability, and internal cues generated by the circadian clock. Changes in the rate of growth within the course of a day have been observed in the leaves, stems, and roots of numerous species. However, the relative impact of the circadian clock on the growth of grasses has not been thoroughly characterized. We examined the influence of diurnal temperature and light changes, and that of the circadian clock on leaf length growth patterns in Brachypodium distachyon using high-resolution time-lapse imaging. Pronounced changes in growth rate were observed under combined photocyles and thermocycles or with thermocycles alone. A considerably more rapid growth rate was observed at 28°C than 12°C, irrespective of the presence or absence of light. In spite of clear circadian clock regulated gene expression, plants exhibited no change in growth rate under conditions of constant light and temperature, and little or no effect under photocycles alone. Therefore, temperature appears to be the primary cue influencing observed oscillations in growth rate and not the circadian clock or photoreceptor activity. Furthermore, the size of the leaf meristem and final cell length did not change in response to changes in temperature. Therefore, the nearly five-fold difference in growth rate observed across thermocycles can be attributed to proportionate changes in the rate of cell division and expansion. A better understanding of the growth cues in B. distachyon will further our ability to model metabolism and biomass accumulation in grasses.

Environmental cues induce changes of steviol glycosides contents and transcription of corresponding biosynthetic genes in Stevia rebaudiana

“…Plant growth and secondary metabolism are commonly regulated by external cues such as light, temperature and water availability (Matos et al, 2014;Ramakrishna and Ravishankar, 2011). In this study, the changes of SGs contents and the transcript levels of corresponding biosynthetic genes were investigated in different temperature, dehydration treatment, photoperiods, and growing stages.…”

Applying hyperspectral imaging to explore natural plant diversity towards improving salt stress tolerance

“…Analysis of color parameters, geometric and morphological characteristics can be done by the operation of VIS cameras in the phenotyping system (Tessmer et al, 2013, Yang et al, 2014. Near-infrared (NIR) light can be recognized by infrared (IR) cameras with usage for night imaging processing (Matos et al, 2014). Some regions of NIR light and shortwave infrared (SWIR) can be identified by NIR cameras that can be used for estimation of leaf water content (Seelig et al, 2008).…”

Integrated “omics” approaches to sustain global productivity of major grain legumes under heat stress

“…The chlorophyll fluorescence ( Fv/Fm ) under HS has been implicated in wheat as an important parameter to assess HS tolerance (Haque, Kjaer, Rosenqvist, Sharma, & Ottosen, ; Sharma, Andersen, Ottosen, & Rosenqvist, , ; Shirdelmoghanloo, Cozzolino, Lohraseb, & Collins, ). Likewise, digital camera‐based devices, viz infrared (IR) cameras deployed for night imaging (Matos et al., ), thermal infrared (TIR) cameras used to measure leaf temperature (Sirault, James, & Furbank, ), NIR cameras to measure leaf water content (Seelig et al., ), are worth mentioning HTPP devices used under various abiotic stresses including HS in plant (for details, see Fahlgren et al., ). To avoid laboratory‐based testing of heat tolerance, “heat tolerance testing system” (HTTS) has been introduced to measure the impact of HS in situ under “natural solar irradiation” condition (Buchner, Karadar, Bauer, & Neuner, ).…”