Of the organisms that perform photosynthesis (Plants) , what is the level of organisation of their body?

Photosynthesis is performed by small plants such as algae and bryophytes which are the simplest plants. In algae, plant body is thallus without any differentiation into root, stem and leaves. They have mostly cellular level of organisation. In bryophytes, vascular tissues and roots are absent.
Higher plants such as angiosperms, gymnosperms perform photosynthesis and plant body is differentiated into stem, root and leaves. Thus, higher plants have mostly tissue/organ level of organisation.