Published: March 20th, 2019
We present a methodology to quantify the starch content in the ovary primordia in sweet cherry (Prunus avium L.) during winter dormancy by using an image analysis system combined with histochemical techniques.
Changes in starch in small structures are associated with key events during several plant developmental processes, including the reproductive phase from pollination to fertilization and the onset of fruiting. However, variations in starch during flower differentiation are not completely known, mainly due to the difficulty of quantifying the starch content in the particularly small structures of the flower primordia. Here, we describe a method for the quantification of starch in the ovary primordia of sweet cherry (Prunus avium L.) by using an image analysis system attached to the microscope, which allows relating the changes in starch content with the different phases of dormancy from autumn to spring. For this purpose, the dormancy status of flower buds is determined by evaluating the bud growth of shoots transferred to controlled conditions at different moments in winter time. For the quantification of starch in the ovary primordia, flower buds are sequentially collected, fixed, embedded in paraffin wax, sectioned, and stained with I2Kl (potassium iodide-iodine). Preparations are observed under the microscope and analyzed by an image analyzer that clearly distinguishes starch from the background. Starch content values are obtained by measuring the optical density of the image that corresponds to the stained starch, considering the sum of the optical density of each pixel as an estimation of the starch content of the frame studied.
Temperate woody perennials adapt to the seasons by modulating their growth and development. While they develop during spring and summer, they stop growing during the autumn to go dormant in winter1. Although dormancy allows them to survive at low winter temperatures, chilling is a prerequisite for a proper budburst in spring2. The important implications of dormancy in temperate fruit production and forestry have led to diverse efforts to determine and predict the dormancy period3. In fruit tree species, empirical experiments transferring shoots to forcing conditions and statistical predictions bas....
1. Dormancy Determination and Plant Material Collection
Dormancy studies require the determination of the moment when the chilling requirements are fulfilled. Despite the lack of phenological changes during winter under field conditions (Figure 1A), cherry trees do not recover the capacity of growth in suitable conditions until they pass a certain period under low temperatures. The regular transference of shoots to a controlled conditions chamber (Figure 1B) during winter time allowed.......
Dormancy in woody perennials presents clear implications in fruit production and forestry in a changing climate, although the biological process behind dormancy remains unclear. Dormancy studies can be approached from different points of view, but the research looking for a biological marker for winter dormancy has intensified over the last years. However, most attempts to find an unequivocal indicator showing when a bud has broken dormancy have been unsuccessful3. The methodology described herein.......
The authors gratefully thank Maria Herrero and Eliseo Rivas for their helpful discussion and advice. This work was supported by the Ministerio de Economía y Competitividad — European Regional Development Fund, European Union [grant number BES- 2010-037992 to E. F.]; the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria [grant numbers RFP2015-00015-00, RTA2014-00085-00, RTA2017-00003-00]; and the Gobierno de Aragón — European Social Fund, European Union [Grupo Consolidado A12-17R].....
|Paraffin Embedding station
|Bright field microscope
|Image Analysis System
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