Bud and spear development of asparagus under constant temperature

Objectives of our study were to quantify the effects of apical dominance and bud cluster activity on asparagus yield patterns and to collect data for process-oriented modeling of the asparagus crop. Plants were grown in 40 L containers. After four years the soil above the asparagus crowns was removed and the containers were placed in a growth chamber at 20°C for three months. During this time, spear length was measured daily except at weekends, and spears were cut when longer than 25 cm. Each spear was assigned to a bud cluster, defined as a dense group of buds clearly distinct from other bud groups on the crown. Although temperature was constant, several properties measured in this study changed during the experiment. The number of active bud clusters first increased then decreased, the lag time between spears growing at the same cluster increased, and the relative growth rate of spears decreased. The constant increase of harvested spears per plant stopped abruptly when the plants ran out of viable buds. At the crop level, i.e. the average for all plants, which is normally monitored in field trials, the transition from linear yield increase to zero increase was less abrupt since plants stopped growing spears on different dates. In our study asparagus yield, i.e. the number of harvested spears, was not limited by low carbohydrate in storage roots, but by a lack of viable buds. This was concluded from the abrupt halt in spear production observed in all plants despite the fact that some plants still had considerable carbohydrate content.

An early-morning gene network controlled by phytochromes and cryptochromes regulates photomorphogenesis pathways in Arabidopsis

Light perception at dawn plays a key role in coordinating multiple molecular processes and in entraining the plant circadian clock.The Arabidopsis mutant lacking the main photoreceptors,however,still shows clock entrainment,indicating that the integration of light into the morning transcriptome is not well understood.In this study,we performed a high-resolution RNA-sequencing time-series experiment,sampling every 2 min beginning at dawn.In parallel experiments,we perturbed temperature,the circadian clock,photoreceptor signaling,and chloroplast-derived light signaling.We used these data to infer a gene network that describes the gene expression dynamics after light stimulus in the morning,and then validated key edges.By sampling time points at high density,we are able to identify three light-and temperature-sensitive bursts of transcription factor activity,one of which lasts for only about 8 min.Phytochrome and cryptochrome mutants cause a delay in the transcriptional bursts at dawn,and completely remove a burst of expression in key photomorphogenesis genes(HY5 and BBX family).Our complete network is available online(http://www-users.york.ac.uk/∼de656/dawnBurst/dawnBurst.html).Taken together,our results show that phytochrome and cryptochrome signaling is required for fine-tuning the dawn transcriptional response to light,but separate pathways can robustly activate much of the program in their absence.