MSGID: 1:317/3 6476cd96   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Light conveyed by the signal transmitting molecule sucrose controls   
   growth of plant roots    
      
     Date:   
         May 30, 2023   
     Source:   
         University of Freiburg   
     Summary:   
         Researchers shows how information about the quantity of absorbed   
         light passes from the leaves to the roots. Photosynthetic sucrose   
         not only supplies roots with carbohydrates but also acts as a   
         signal transmitter for light-dependent root architecture.   
      
      
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   FULL STORY   
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   Researchers shows how information about the quantity of absorbed light   
   passes from the leaves to the roots. Photosynthetic sucrose not only   
   supplies roots with carbohydrates but also acts as a signal transmitter   
   for light-dependent root architecture.   
      
   Plant growth is driven by light and supplied with energy through   
   photosynthesis by green leaves. It is the same for roots that grow in   
   the dark -- they receive the products of photosynthesis, in particular   
   sucrose, i.e. sugar, via the central transportation pathways of   
   phloem. Dr. Stefan Kircher and Prof. Dr.   
      
   Peter Schopfer from the University of Freiburg's Faculty of Biology have   
   now shown in experiments using the model plant Arabidopsis thaliana (thale   
   cress) that the sucrose not only guarantees the supply of carbohydrates   
   to the roots, it also acts as a signal transmitter for the formation of   
   light-dependent root architecture. It does this in two ways: firstly,   
   sucrose directly guides elongation of the primary root. Secondly, the   
   sucrose that is transported to the tip of the root then regulates the   
   production of the plant hormone auxin.   
      
   This hormone drives the rate of formation of new lateral roots, which   
   along with elongation of the primary root is synchronised by the joint   
   signal transmitter.   
      
   "This enables the root growth to adapt to the current photosynthesis   
   performance of the leaves as light and other environmental conditions   
   change, for example on the change from day to night," says Kircher.   
      
   Experimental evidence To demonstrate that the sucrose produced through   
   photosynthesis is the decisive signal transmitter, Kircher and Schopfer   
   placed the plants in a room with light but with no carbon dioxide (CO2)   
   in the air, thus making photosynthesis impossible. The outcome was that   
   no more lateral roots were formed. This result was confirmed by another   
   experiment in which the two biologists treated either the leaves or   
   the roots in the dark with a solution of sucrose. In both approaches,   
   lateral roots developed the same as in control plants which were exposed   
   to light. "These results show that the production of sucrose in leaves   
   is necessary for the formation of lateral roots. And it confirms the   
   hypothesis that sucrose acts as a signal transmitter for light stimuli,"   
   says Kircher.   
      
   Activation of auxin biosynthesis by sucrose signal In earlier studies,   
   researchers had already shown that the auxin produced in the roots   
   from the amino acid tryptophan drives the rate of development of new   
   lateral roots. Kircher and Schopfer have now shown how sucrose triggers   
   this process. To do this, they placed the plants in a dark room for two   
   days and carried out various experiments to discover their influence on   
   the formation of lateral roots. Administering tryptophan to the roots   
   at the same time as treating the leaves with sucrose had the greatest   
   effect. By contrast, tryptophan had little effect if it was applied to   
   the leaves or without sucrose at the roots. "These observations confirm   
   that the sucrose produced through photosynthesis serves as a trigger   
   for the synthesis of auxin," says Kircher.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Endangered_Plants # Botany # Food_and_Agriculture   
                   # Nature   
             o Earth_&_Climate   
                   # Global_Warming # Sustainability # Environmental_Issues   
                   # Air_Quality   
       * RELATED_TERMS   
             o Root_vegetable o Ginger o Nicotine o Pupil o Leaf o Herbal_tea   
             o Chlorophyll o Ultraviolet   
      
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   Story Source: Materials provided by University_of_Freiburg. Note:   
   Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Stefan Kircher, Peter Schopfer. Photosynthetic sucrose drives   
      the lateral   
         root clock in Arabidopsis seedlings. Current Biology, 2023; DOI:   
         10.1016/ j.cub.2023.04.061   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230530174307.htm   
      
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