For example, a herbaceous plant:

Central System:

Meristems: These zones of actively dividing cells are located at the tips of shoots and roots and are responsible for generating new tissues. Meristematic zones.

Vascular system: This network transports water, nutrients, and signaling molecules throughout the plant.

Signals:

1. Stress receptors, release chemicals under stress
2. Wound receptors, release chemicals when wounded
3. Hormone receptors, release chemicals in response to the environment

Triggered by stress, wounds, light, temperature, nutrient availability and so on...

Graded electrical potentials can also act as communication and control of many process.