Agar with embedded channels to study root growth

Abstract

Agar have long been used as a growth media for plants. Here, we made agar media with embedded fluidic channels to study the effect of exposure to nutrient solution on root growth and pull-out force. Black eye bean (Vigna Unguiculata) and Mung bean (Vigna Radiata) were used in this study due to their rapid root development. Agar media were fabricated using casting process with removable cores to form channels which were subsequently filled with nutrient solution. Upon germination, beans were transplanted onto the agar media and allowed to grow. Pull-out force was determined at 96, 120 and 144 h after germination by applying a force on the hypocotyl above the gel surface. The effect of nutrients was investigated by comparing corresponding data obtained from control plants which have not been exposed to nutrient solution. Pull-out force of Black Eye bean plantlets grown in agar with nutrient solution in channels was greater than those grown in gel without nutrients and was 110% greater after 144 h of germination. Pull-out force of Mung bean plantlets grown in agar with and without nutrient solution was similar. tap root lengths of Black eye bean and Mung Bean plantlets grown in agar with nutrient solution are shorter than those grown without nutrient. "Kanten", as agar is known in Japanese, was first discovered from extracts of marine macroalgae, commonly known as seaweed, by Minoya Torazaemon in 1658 1. Coastal communities in Asia including those in Malay Archipelago of South East Asia have long been extracting agar from genus Gracilaria as a food source. The name "agar" derives from the Malay lexicon to describe jelly(gel)-based food. "Agar" has more in common to "algae" from which the agar hydrogels are obtained. At the present time, production of agar from Gracilaria accounts for 14% of global seaweed aquaculture production with China, Indonesia, Malaysia, Philippines and Vietnam being major producers 2. Agar are polysaccharides with excellent hydrocolloidal properties suitable for many industrial applications 3. Favorable attributes of agar include low production cost compared to alternative materials and ability to form reversible gels with acceptable mechanical properties at low concentration which is useful for applications in healthcare 4-6. Furthermore, agar can be easily blended with other polymers to form composites with superior properties. Composite hydrogels of agar and gelatin have sufficient mechanical properties while blending with alginates results in smart hydrogels which respond to pH 7,8. Plant culture media contain nutrients, vitamins and other supplements needed for plant growth and development. Agar media is a suitable matrix for plant culture as agar are not digested by plant enzymes and do not react with supplements 9. Plant culture media were developed from well-established bacteria growth media by adding nutrients needed to facilitate plant growth and development. Murashige and Skoog for example supplemented White's modified agar medium with kinetin and indole acetic acid and observed yi...

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