Final answer:
Water serves as a determining factor for the number of plants in the desert, given its essential role in photosynthesis, cell production, and nutrient transportation. It majorly influences plant distribution and the net primary productivity of the biome. Evaporation, affected by factors like wind, also impacts water availability for desert plants.
Step-by-step explanation:
The number of plants in the desert is closely linked to the amount of water available. Given water's critical roles in plant growth, including its use as a reagent in photosynthesis, a constituent of new cells, and as a medium for nutrient transport, water is the most important factor limiting terrestrial photosynthesis worldwide, especially in arid regions like deserts. Since water availability directly determines the survival and distribution of organisms in such habitats, in response to the question, water is best described as a (a) Determining factor for the number of plants in the desert.
Moreover, aspects such as water conservation strategies of desert plants, like having smaller leaves to reduce evaporation, underline the importance of water as an abiotic factor. Temperature and moisture together influence the net primary productivity of a biome, which is an estimation of the biomass available as food for other organisms.
Factors like wind also play a significant role because they affect the rate of evaporation and transpiration, further influencing the amount of water accessible to plants. Understanding these interactions is vital in comprehending the dynamics of desert ecosystems.