Number 6 grows on planets with low gravity, the thin stem easily able to support the shell on top. When threatened, the shell sucks up the stem, pulling itself tight against the ground. The shell is also translucent to allow light to reach the leaves.
Number 2 records sounds and plays them back. By imitating the calls of predators, they can scare away herbivores. The plant cannot think to tell the difference between different animal sounds, aircraft, or the wind, but it learns what works through trial and error. Human voices have been recorded and then passed from plant to plant through the generations, the population still reciting presidential speeches from centuries ago (with some differences due to the build up of minor errors). The musical gardens made of these plants have become a major tourist attraction in the 27th century.
Number 4 sheds its leaves every winter. This specimen has one left.
Number 1 is a heavily calcified flower. Its bony consistency deters most herbivores.
Number 5 has blisters of foul-tasting liquid on the outside. These blisters are harvested by ant-like creatures to protect their nests from anteater-like creatures.
Number 7 is actually a fungous.