Select the incorrect statement.

• A

  Plants growing in tropical rain forest show lower temperature optimum than plants growing in temperate deciduous forest.

• B

  Light is rarely a limiting factor in nature except for plants growing in shade or in dense forest.

• C

  The ${\mathrm{C}}_3$and ${\mathrm{C}}_4$ plants respond differently to ${\mathrm{CO}}_2$ concentrations.

• D

  The effect of water as a factor is more through the plant, rather than directly on photosynthesis.