Final answer:
Condition ψsoil < ψroot < ψleaf < ψatm is required for the movement of water from soil to atmosphere through a plant, driven by decreasing water potential, with transpiration assisting in water's exit through the leaves.
Step-by-step explanation:
For a continued movement of water from the soil into and through a plant via transpiration, the condition required is ψsoil < ψroot < ψleaf < ψatm. This reflects the gradient of water potential, where water potential decreases from the soil (ψsoil) to the root (ψroot), ascending up through the plant to the leaf (ψleaf), and finally to the atmosphere (ψatm). Water moves towards the region of lower water potential, facilitating its flow from the soil to the atmosphere through the process of transpiration.
Water enters the plant through the root hairs due to the negative water potential, which draws water into the roots. Through cohesion and adhesion, water is then drawn up the plant's vascular system, and ultimately, transpiration pulls water from the leaves when it exits through the stomata.
It is important to note that dry soil has a higher water potential compared to wet soil. However, under drought conditions, the stomata may close to conserve water, altering the normal transpiration flow.