Figures (3)  Tables (2)

    • Figure 1.  Conceptual model of various effects of microplastic on crops. Positive (+ve) effect related to microfibers in onion and carrot[14,24], lethal effect linked to biodegradeable plastic in wheat, ryegrass and maize[8,25,26], toxic effect related to low-density polyethylene in wheat[8], high-density polyethylene in ryegrass[25], polystyrene fluorescent in broad bean[27], PVC, polyethylene in lettuce[12,16,26], and no effect associated to polystyrene fluorescent in wheat[28].

    • Figure 2.  Cumulative publications numbers on microplastic consequences and direct toxicity for food crops.

    • Figure 3.  Diagram disclosing various mechanisms through which microplastic can affect ecosystem functions and plant performance. Blue arrows show observed effects in previous studies while white arrows show conceptual mechanisms.

    • AdditivesPolymersReference
      Irgafos 168 (tris (2,4-ditert-butylphenyl) phosphite)Polyethylene and
      Polypropylene      		[19]
      Diisoheptylphthalate, Benzyl butyl phthalate, Di butyl phthalate, dipentyl phthalate, di-(2-ethylhexyl) adipate, di-octyladipate, diethyl phthalates, diisobutylphthalate, Tris (2 chloroethyl) phosphate, dicyclohexyl phthalate, butyl benzyl phthalate, diheptyl adipate, and heptyl adipatePolyvinylchloride[20,21]
      Irganox 1010 (tetrakismethylene-(3,5-di-t-butyl-4- hydroxyhydrocinnamate) methane)Linear low-density polyethylene and
      High-density polyethylene      		[20]

      Table 1.  Examples of additives released from different polymers.

    • Crops PolymersObserved effect directions
      (+, –) for crop growth      		Expected category
      TolerantSensitive
      OnionPolystyrene, polyethylene terephthalate, polyamide, microfiber polyester+√
      CarrotMicrofibers: polyester, polyamide, polypropylene+**
      WheatLow-density polyethylene, biodegradable polylactic-acid–√
      MaizePolyethylene, biodegradable polylactic-acid–√
      RyegrassBiodegradable polylactic-acid–√
      Broad beanPolystyrene fluorescent–√
      LettucePolyethylene–√
      * unclear.

      Table 2.  Hypothesized classification of different crops based on their observed responses to polymers (Fig. 1).