Biomass partitioning

Biomass partitioning is the process by which plants divide their energy amongst their parts. For example, there may be a tradeoff in proteins and carbohydrates allocated towards leaves for photosynthesis or to roots for the process of nutrient uptake.The study of biomass partitioning is important to crop growth. The percentages of partitioning can be determined with the equation ( d W / d t ) i = P c i ∗ d W / d t with dW/dt is the growth rate (dW/dt)_i and P_ci are the rates of biomass partitioned and the respective partitioning factor for each plant organ i.

Overall, nitrogen availability has a strong effect on partitioning, with plants growing in low-nitrogen areas partitioning most of their biomass to underground structures. Soil nitrogen availability is a strong determinant of biomass allocation. For example, in low productivity systems such as boreal forests, trees devote a large portion of their biomass to roots. But as the soil productivity begins to increase, biomass is primarily allocated to aboveground structures such as leaves and stems. As an overall pattern, the overall lengths of roots begin to decrease as nitrogen concentrations increase.

In addition to nitrogen as a factor of plant biomass partitioning, other environmental stressors such as water availability play a role. For example, plants that are growing in dry conditions often have a decreased total biomass production but they also contribute more of their biomass to the roots and develop a higher root:shoot. When plants allocate more of their biomass to their roots, they are able to enhance water absorption by tapping further down into the water table as well as extending further laterally with the aid of increased root hairs. But, when there is an extreme soil drought, there is not an increase in root:shoot biomass. This suggests that there is a limit to which plant biomass allocation responds to water stress and possibly other environmental factors as well. It is important for plants to be able to balance their absorption and utilization processes with differing water and nitrogen availabilities because they adjust their growth in order to accommodate the abundances of growth-limiting resources, such as water and nitrogen.