Laura Hillmann1, Mokhles Elsysy1,2, Charity Goeckeritz1, Courtney Hollender1, Nikki Rothwell3, Michael Blanke4, Todd Einhorn5. 1. Department of Horticulture, Michigan State University, Plant and Soil Sciences Bldg., 1066 Bogue Street, East Lansing, MI, 48824, USA. 2. Department of Pomology, College of Agriculture, Assiut University, Assiut, 71515, Egypt. 3. Northwest Michigan Horticultural Research Center, Michigan State University, 6686 S. Center Highway, Traverse City, MI, USA. 4. Rheinische-Friedrich-Wilhelms-Universität Bonn, INRES Gartenbauwissenschaft, Auf dem Huegel 6, Bonn, Germany. 5. Department of Horticulture, Michigan State University, Plant and Soil Sciences Bldg., 1066 Bogue Street, East Lansing, MI, 48824, USA. einhornt@msu.edu.
Abstract
MAIN CONCLUSION: Growing degree hours (GDH) predicted floral bud development of 'Montmorency' sour cherry and explained changes in lethal temperatures (LT50) that preempted any visible changes in bud phenology. The gradual warming during late winter and early spring promotes floral bud development and, concomitantly, the de-acclimation of Prunus sp. flowers. In fact, once ecodormancy releases, an approximate 20 °C loss of hardiness occurs prior to any distinguishable changes in external bud phenology. The aim of the following work was to characterize the physiological changes of 'Montmorency' sour cherry floral buds as they transition from endo- and ecodormancy and resume growth, and to determine whether physiological and anatomical characteristics within the buds preempt or signify dormancy release to enable a better prediction of freeze susceptibility. Here, we present a developmental timeline of the preanthesis changes of 'Montmorency' floral buds, ovaries and anthers over 2 years following their completion of chilling and relate these changes to growing degree hours (GDH) and the lethal temperature (LT50) of flowers. Changes in bud dry weight (DW), fresh weight (FW), volume, and external phenology stage including the percentage of green color development of bud scales were predicted by heat accumulation but were not early predictors of the increasing freeze susceptibility of pistils. Between endodormancy and green tip stage, ovary volume increased nearly threefold and relative water content (RWC) increased from ~ 45 to 70% in both years. A linear mixed regression model indicated that RWC and the interaction between RWC and ovary growth were significant predictors of LT50. Importantly, the loss of ~ 20 °C of freeze resistance occurred between 45 and 57% RWC and preceded any detectable changes in bud phenology. Microsporogenesis was observed after dormancy release when measurable changes in the ovary and bud RWC had already occurred. A GDH model estimated freeze sensitivity of pistils and explained 93% of the variation in LT50 during preanthesis development. A simple GDH model to predict critical freeze temperature of pistils should aid producers to manage frost protection.
MAIN CONCLUSION: Growing degree hours (GDH) predicted floral bud development of 'Montmorency' sour cherry and explained changes in lethal temperatures (LT50) that preempted any visible changes in bud phenology. The gradual warming during late winter and early spring promotes floral bud development and, concomitantly, the de-acclimation of Prunus sp. flowers. In fact, once ecodormancy releases, an approximate 20 °C loss of hardiness occurs prior to any distinguishable changes in external bud phenology. The aim of the following work was to characterize the physiological changes of 'Montmorency' sour cherry floral buds as they transition from endo- and ecodormancy and resume growth, and to determine whether physiological and anatomical characteristics within the buds preempt or signify dormancy release to enable a better prediction of freeze susceptibility. Here, we present a developmental timeline of the preanthesis changes of 'Montmorency' floral buds, ovaries and anthers over 2 years following their completion of chilling and relate these changes to growing degree hours (GDH) and the lethal temperature (LT50) of flowers. Changes in bud dry weight (DW), fresh weight (FW), volume, and external phenology stage including the percentage of green color development of bud scales were predicted by heat accumulation but were not early predictors of the increasing freeze susceptibility of pistils. Between endodormancy and green tip stage, ovary volume increased nearly threefold and relative water content (RWC) increased from ~ 45 to 70% in both years. A linear mixed regression model indicated that RWC and the interaction between RWC and ovary growth were significant predictors of LT50. Importantly, the loss of ~ 20 °C of freeze resistance occurred between 45 and 57% RWC and preceded any detectable changes in bud phenology. Microsporogenesis was observed after dormancy release when measurable changes in the ovary and bud RWC had already occurred. A GDH model estimated freeze sensitivity of pistils and explained 93% of the variation in LT50 during preanthesis development. A simple GDH model to predict critical freeze temperature of pistils should aid producers to manage frost protection.
Authors: Sara Herrera; Jorge Lora; Erica Fadón; Afif Hedhly; José Manuel Alonso; José I Hormaza; Javier Rodrigo Journal: Front Plant Sci Date: 2022-04-07 Impact factor: 6.627