var_name --> [amount,of], substance, in_plant.
var_name --> [amount,of], substance, in_physical.
var_name --> [rate,of], plant_process, in_plant.
var_name --> [rate,of], physical_process, in_physical.
in_plant --> [in], plant, plant_part.
in_plant --> [].
in_physical --> [in], physical.
in_physical --> [].
substance --> [biomass].
substance --> [water].
substance --> [carbon].
substance --> [nitrogen].
substance --> [phosphorus].
plant_process --> [photosynthesis].
plant_process --> [assimilation].
plant_process --> [net,assimilation].
plant_process --> [gross,assimilation].
plant_process --> [respiration].
plant_process --> [growth].
physical_process --> [precipitation].
physical_process --> [transpiration].
physical_process --> [evaporation].
physical_process --> [evapotranspiration].
physical_process --> [drainage].
physical_process --> [overlandflow].
plant --> [plant].
plant --> [tree].
plant --> [crop].
plant --> [weed].
physical --> [soil].
physical --> [soil,layer].
physical --> [lake].
physical --> [river].
plant_part --> [leaf].
plant_part --> [branch].
plant_part --> [stem].
plant_part --> [root].
plant_part --> [seed].
plant_part --> [].