Refer to your graph of productivity and light intensity. At what light intensity do you expect there to be no net productivity? No gross productivity? Table 4Gross productivity(mg/L/hr)Net productivity(mg/L/hr)Test tube% Light2.381.52100%-1.412|-2.28-3.62- 3.89-3.96365%25%.174-0.95-.1710%6.2%LO

Plants do photosynthesis and makes the food available for them as well as for consumers.to sustain the regular maintainace of the ecosystem.and this energy is transferred from one trophic level to another trophic level throgh ecosystem. Here the gross primary productivity means the rate at which the amount of energy produced and stored by different producers is called the gross primary productivity. Simply we can say total amount of product of photosynthesis is called gross primary productivity. Whereas on the other hand the Net primary productivity includes energy produced and stored by plants as well as energy consumed and stored by the consumers is called as Net primary productivity.therefore The Net primary productivity and Gross primary productivity of an ecosystem provides an Idea about the availavility of resources in the ecosystem.Generally the Net primary productivity and gross primary productivity of an ecosystem has zero value upto the light intensity of 25%. Here, in the above graph, there is no Gross productivity at light intensities of 2%,10%, 25% because the productivity is -0.17, -0.95,0.17 respectively and the Gross productivity cannot be negative. Whereas, there is no Net productivity is seen in any light intensity. The value of all net productivities are negative.