Prolog for simple grammar

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   --> [].