The very primitive plants like and include algae, liverworts and mosses, are ‘non’ vascular’, in that they do not have internal systems to carry water. Their cells are not very 'differentiated' into leaves stems and roots, but are all similar.

Plants are said to be 'vascular' when they have internal water-carrying systems. These consist of tissues called xylem to transport water up, while tissue called phloem moves food downward from the leaves to roots. [CH6] Xylem is very strong to hold the water, and is the woody part – laden with ‘lignin’. This is important compound proved hard to breakdown. Phloem tissue is usually outside that and consist of starch-filled plastids.

Stems move water and nutrients to the plant's leaves and the leaves capture the sunlight the plant needs for photosynthesis These all grow in boggy conditions often on rocks/silt/water edges. They also grew some roots – and rhizomes - to take up water and nutrients and help anchor them to any cracks and crevices and accumulations of debris.

Plant rhizomes play important roles in [CH8] shaping Earth’s environments by reducing soil erosion rates and thereby increasing the stability of land surface and resilience of plant communities. Rhizomes more likely to stabilise surface – important, but not likely to grow deeply. The complex, belowground rhizome systems of a plant around this time has exposed their contribution to the formation of the earliest record of rooted red-bed soils in Asia A club moss lycopsid.appears to an immediate colonizer of any newly formed alluvium - deposit of clay, silt, and sand left by flowing floodwater. The continuous growth of a lycopsid via their rhizomes, and sequential burial in fine sediments, may have conferred erosion resistance to floodplains and contributed to the establishment of red-bed paleosols. Although these plants have limited xylem and wide cortex tissues, the rhizomatous growth of this plant could produce dense vegetation cover which would have protected the substrate against surface erosion while increasing trapping of fine particles. Perhaps more importantly, belowground rhizomes formed complex networks of aerial stems coming to ground with rhizomes, which could bind sediments in a reinforced matrix, thereby increasing soil aggregate stability (Xue et al 2016)

Roots could spread and rhizomes could trap particles, leading to increased stabilisation of ground away from water.

Vascular plants evolved true roots made of vascular tissues. Compared with rhizoid, roots can absorb more water and minerals from the soil.

Water delivery is the key to survival. For plants this is through the roots, which need support. The further the roots can grow, the more available water and nutrients. The roots of seed plants became increasingly different from the other plant cells, the stem and leaves.

How did roots push through the hard sediments and gain nutrients? Roots could grow better after flooding, fungi grew with the roots, extending the reach of the roots. In exchange for the energy, the fungi provided minerals to the plants. Bacteria would also have been around, as they can live off hydrogen and oxygen. They didn’t need organic matter in the first instance, but once it was around, they would have soon made use of exudates – glomalin - from the roots.

Rooting would have stopped erosion, in the same way that the spore plants did. Previously any mineral erosion from rocks would have gone straight the water. Now they could be held by the roots, thereby providing means for further growth. (What would have been the necessary minerals then?) Slowing water movement was crucial for development of stable and a soil environment. soils.

While there are now many studies concerning interactions between AM fungi and bacteria, the underlying mechanisms behind these associations are in general not very well understood, and their functional properties still require further experimental confirmation.  Most plant roots are colonized by mycorrhizal fungi and their presence also generally stimulates plant growth. However, the beneficial traits of root-colonizing bacteria and fungi have been mainly studied separately. Only recently have the synergistic effects of bacteria and mycorrhizal fungi been studied with respect to their combined beneficial impacts on plants.” Some bacteria have been shown to directly affect AM fungal germination and growth rate” (Artursson et al 20) 

In addition to their properties of capturing nitrogen, solubising phosphates, and helping build aggregates, other bacteria help to produce plant hormones such as auxins, and are known as plant-growth promoting rhizobacteria (PGPR). It is clear the relation between bacteria and plants will have played an important role of the co-development of plants and soil in the early days.It seems that auxins and Cytokinins emerged early in the algal ancestors, while gibberellins came later in the bryophytes (Wang, et al., 2015)

PGPRs

Plant growth promoting rhizobacteria (PGPRs)influence plant growth and development by the production of phytohormones such as auxins, gibberellins, and cytokinins.”Little is known on the genetic basis and signal transduction components that mediate the beneficial effects of PGPRs in plants.” (Ortiz-Castro, Valencia-Cantero, and Lopez-Bucio, 2008).

Plant growth and development are critically influenced by unpredictable changes in their environments, so plants have had to develop robust adaptive mechanisms. Dynamic auxin and cytokinin pathways regulate a plethora of developmental processes, and their crosstalk mediates stress responses, along with other crucial signalling molecules, called reactive oxygen species (ROS) (Bielach, Hrtyan, and Tognetti, 2017)

Bacteria, now found in rhizosphere in wetlands, “have also been reported to produce plant hormones such as IAA, the most common plant hormone of the class of auxins. IAA is responsible for the division, expansion and differentiation of plant cells and tissues and also stimulates root elongation” (Nacoon et al., 2020). Presumably this did not happen until there were roots ie now.

Cytokinins influence many processes like growth, nutrient responses and the response to biotic and abiotic stresses. Cytokinins are an example of the importance of the vascular system, as they are transported from roots to shoots via the xylem and from shoots to roots via the phloem. The cytokinin signal transduction pathway is similar to that found in bacterial two-component signalling systems, which bacteria sense and respond to environmental stimuli (Kierber and Eric Schaller, 2018)

The phytohormone cytokinin plays diverse roles in plant development, influencing many processes like growth, nutrient responses and the response to biotic and abiotic stresses. Cytokinin levels in plants are regulated by biosynthesis and inactivation pathways. Cytokinins are picked up by receptors that activate a family of transcription factors in the nucleus. Cytokinins are transported from roots to shoots via the xylem and from shoots to roots via the phloem. The cytokinin signal pathway involves a ‘phosphorelay’ similar to that in bacterial signalling systems, used to sense and respond to environmental stimuli (Kierber and Eric Schaller, 2018). The two key components in these bacterial signalling systems are a sensor in their membrane that picks up environmental stimuli, and a response that propagates the signal often directly copying the target genes. Despite the enormous progress made in understanding cytokinin metabolism and signalling, important questions remain.

TIR is a protein domain, a sort of enzyme that helps in internal sigmalling. (Jacob et all 2022). They are made of around 150 amino acids, that helps in the defence of most organisms again various attacks. The first TIR domain protein architecture is present in prokaryotes, oomycetes, plants, and animals (Lapin et al., 2022). Certain TIRs are present in multiple land plants including bryophytes, indicating they have been conserved for over 500 my. Plant TIR-based signalling is emerging as central to the potentiation and effectiveness of host defences. Equally relevant for plant fitness are mechanisms that limit potent TIR signalling in healthy tissues but maintain their preparedness for infection (Lapin et al., 2022). Increased knowledge of how plants fine-tune their stress pathways in nature is now of fundamental interest in improving crop performance.