Photothermal controls of vegetative dormancy in Poa secunda

Abstract

Background Summer vegetative dormancy is a desirable trait in cool‐season grasses when they are interplanted with annual crops. Sandberg bluegrass (Poa secunda J. Presl.) shows summer dormancy, but the environmental cues that control dormancy remain unknown. Methods A controlled environment study using temperature and day length combinations of 32.2°C/15 h, 26.6°C/14 h, 21.1°C/13 h, and 15.5°C/12 h was conducted with P. secunda accessions PI232347, PI639272, and PI232348, and ‘Audubon’ red fescue as a nondormant control to determine the optimum treatment for dormancy induction. A second study using treatments of 26.6°C/14 h, 21.1°C/13 h, and 15.5°C/12 h was conducted to determine the thresholds for dormancy release. A third study used a factorial experiment with two temperatures (32.2°C and 15.5°C) and two day lengths (15 and 12 h) to differentiate between temperature and day length effects on dormancy induction. Results Of the four temperature and day length combinations, all except for 15.5°C/12 h resulted in dormancy by the end of 6 weeks, with 32.2°C/15 h inducing dormancy in only 17 days. Of the three treatments for dormancy release, 15.5°C/12 h broke dormancy the fastest in all accessions and released the most number of plants from dormancy. Considerable variation existed between accessions for the speed of dormancy release in the 21.1°C/13 h and 26.6°C/14 h treatments. The third study showed that temperature is the primary inducer for summer dormancy, while longer day length may promote dormancy under inductive temperatures. Conclusions This study identified the optimum photothermal for induction and release of summer dormancy in P. secunda, which will help future studies in elucidating the mechanism of summer dormancy.

Atmospheric drying and soil drying: Differential effects on grass community composition

“…This further emphasizes the potential importance and strength of the drought dormancy strategy for this species (and for this system). Recent work has also shown that P. secunda may enter and break dormancy in response to temperature and photoperiod (potentially more than soil moisture, Chen et al., 2022). Past work in this same experiment (Bio3D) demonstrated how P. secunda can shift energy allocation to invest more in roots at the expense of shoots in combined soil drying and atmospheric drying conditions (Watson et al., 2023).…”

“…This further emphasizes the potential importance and strength of the drought dormancy strategy for this species (and for this system). Recent work has also shown that P. secunda may enter and break dormancy in response to temperature and photoperiod (potentially more than soil moisture, Chen et al, 2022) F I G U R E 3 Nonmetric dimensional scaling (NMDS) ordination of Bray-Curtis dissimilarity among the grass communities under three levels of humidity in dry soils (shades of red) and three levels of humidity in wet soils (shades of blue, k = 3; stress = 0.1; PERMANOVA, interaction term pseudo-F 1,18 = 1.77, r 2 = .2, p = .09). Species labels are located on the ordination based on their species scores and rescaled for visualization with pot communities.…”