The correct answer is - as energy lost at every trophic level.
Explanation:
In any ecological ecosystem the energy pyramids always upright unlike other pyramids such as biomass showing the number of organisms, that can be diamond shape, inverted or upright.
The main reason behind this is due to the fact that it is only a pyramid in the ecosystem that always unidirectional in the food chain which is always some energy lost with an increase in the trophic level in the food chain. This loss of energy always gets back to the atmosphere in each step of the food chain.
The tissue you are referring to here is the xylem, a <u>vascular tissue</u>, whose basic function is to transport water and nutrients from the roots to the rest of the plant.
