Dor Haim _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel; The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Liron Shalom _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Yasmin Simhon _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel; The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Lyudmila Shlizerman _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Itzhak Kamara _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Michael Morozov _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Alfonso Albacete _ CEBAS-CSIC, Department of Plant Nutrition, Campus Universitario de Eapinardo, Espinardo, Murcia, Spain.
Rosa M Rivero _ CEBAS-CSIC, Department of Plant Nutrition, Campus Universitario de Eapinardo, Espinardo, Murcia, Spain.
Avi Sadka _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
In many fruit trees, heavy fruit load in one year reduces flowering in the following year, creating a biennial fluctuation in yield termed alternate bearing AB). In subtropical trees, where flowering induction is mostly governed by the accumulation of chilling hours, fruit load is thought to generate a signal (AB signal) that blocks the perception of the cold induction. Fruit removal during a heavy-fruit-load year (On-Crop) is effective at inducing flowering only if performed one to a few months prior to onset of the flowering induction period. We previously showed that following fruit removal, content of the auxin indoleacetic acid (IAA) in citrus buds is reduced, suggesting that the hormone plays a role in the AB signal. Here, we demonstrate that fruit presence generates relatively strong polar auxin transport (PAT) in citrus and olive stems. Upon fruit removal, PAT is reduced and allows auxin release from the bud. Furthermore, using immunolocalization, hormone and gene expression analyses, we show that in citrus, IAA level in the bud and, specifically, in the apical meristem is reduced upon fruit removal. Overall, our data provide support for the notion that fruit presence generates an auxin signal in the bud which may affect flowering induction.
Dor Haim _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel; The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Liron Shalom _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Yasmin Simhon _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel; The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Lyudmila Shlizerman _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Itzhak Kamara _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Michael Morozov _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
Alfonso Albacete _ CEBAS-CSIC, Department of Plant Nutrition, Campus Universitario de Eapinardo, Espinardo, Murcia, Spain.
Rosa M Rivero _ CEBAS-CSIC, Department of Plant Nutrition, Campus Universitario de Eapinardo, Espinardo, Murcia, Spain.
Avi Sadka _ Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.
In many fruit trees, heavy fruit load in one year reduces flowering in the following year, creating a biennial fluctuation in yield termed alternate bearing AB). In subtropical trees, where flowering induction is mostly governed by the accumulation of chilling hours, fruit load is thought to generate a signal (AB signal) that blocks the perception of the cold induction. Fruit removal during a heavy-fruit-load year (On-Crop) is effective at inducing flowering only if performed one to a few months prior to onset of the flowering induction period. We previously showed that following fruit removal, content of the auxin indoleacetic acid (IAA) in citrus buds is reduced, suggesting that the hormone plays a role in the AB signal. Here, we demonstrate that fruit presence generates relatively strong polar auxin transport (PAT) in citrus and olive stems. Upon fruit removal, PAT is reduced and allows auxin release from the bud. Furthermore, using immunolocalization, hormone and gene expression analyses, we show that in citrus, IAA level in the bud and, specifically, in the apical meristem is reduced upon fruit removal. Overall, our data provide support for the notion that fruit presence generates an auxin signal in the bud which may affect flowering induction.