Introduction

Plants, ranging from distant algae and diminutive mosses to towering sequoia trees, are uniquely morphologically adapted to the specific ecological and climatic niches that they inhabit. In turn, the architectures of prototypical plant structures like leaves, stems, and roots, reflect in their overall form, the specialized capacity to perform specific functions. Likewise, the cells that constitute these various plant organs – though similar to some extent in their organellar composition – manifest, within their surrounding cellular context, distinct anatomies that are evolutionarily tailored to their particular tasks. As such, Charles Darwin aptly remarked that the study of morphology is “the most interesting department of natural history.”

Here you see a moss called Physcomitrella patens that botanists believe are modern representatives of evolutionarily distant plant lineages that first migrated to land from water more than 450 million years ago. This means that we can study Physcomitrella to understand how plants evolved the traits that allowed them to conquer land.

At first glance, you might think that the image on the left is of some bizarre microorganism, but in fact, it is a single-celled green algae called Chlamydomonas reinhardtii. In the tree of plant evolution, these aquatic green algae are considered representatives of the aquatic ancestors of modern day land plants.