Cell-to-cell communication is absolutely essential for multicellular organisms. but how do plants communicate when their cells are surrounded by cell walls? plants use for long-distance signaling, such as ethylene which promotes fruit ripening and regulates growth.

hormones.

Explanation:

Plants can communicate through hormones even though they are surrounded by cell wall. For long distance signaling hormones are used as messengers by plant cells. Plant cells have many cell surface receptors to which these hormones can bind to show response.

For example: Ethylene is a hormone in plants which causes fruit ripening by digesting a hard substance named as middle lamella. Once middle lamella is degraded the fruit becomes soft and said to be ripened. An enzyme known as polygalacturonase is activated by ethylene to cause fruit ripening. An unripened fruit is very hard due to the presence of middle lamella so polygalacturonase needs to be activated to digest it and cause softening.

Solid - definite shape and volume

Liquid - no definite shape but definite volume

Gas - no definite shape or volume

Plasma - high temperature physical state of matter in which atoms lose most of their electrons