Amount of wood produced annually by an are of forest sets a lower limit to annual solar energy input. This is directly proportional to the amount of wood produced by the whole trunk during the year. Dependent not on ring widths alone but influenced by the diameters of the cross sections of trunks on which they accrue. Rainfall Deductions of climate can not be made on growth rings alone. Variation in species and growth sites, successive growth rings differ.
Roots have aeration systems that include aerenchymatous tissues.
These are found within roots that grow under waterlogged conditions. Thickening of the endodermis is reported to play a role in ion selectivity and the development of hydrostatic pressure in the root system. Such features occur in unrelated fossil groups. Mycorrhizal associations - confer greater drought resistance an nutrient access. Confirmed in the fossil record Triassic peat.