How do plant cells speak with eachother?
To work together, communication is important. Just like how we communicate with other people, the cells inside our bodies need to be able to communicate with each other in order to work together. Human cells can communicate via a variety of methods, such as through direct contact as well as by using a special system called the nervous system (which plants do not have). Plants are made up of different types of cells too, and they also need to be able to communicate with all their cells in response to changes such as light, temperature and nutrient availability, to help the plant grow and flower. Plant cells also want to communicate what is happening in their roots, stems, leaves and flowers. So how do plant cells communicate? Before we have a look at how plant cells communicate, let’s have a look at the basic structure of a plant cell.
Plant cells have a nucleus which contains the genetic material of the cell, called DNA, which controls the cell’s activities. When the cell sends signals inside its own cell, this is called intracellular signalling. The cell membrane controls movement of things in and out of the cell. Plant cells also have a cytoplasm, which is a jelly-like material that holds lots of structures called organelles, and nutrients dissolved in its cytoplasm. The organelles in plant cells include structures such as mitochondria for energy and ribosomes for making protein.
Plant cells and animal cells share these similar structures, but plant cells are also unique in their own ways. Plant cells can contain chloroplast organelles, which absorb light energy for photosynthesis. Plant cells are also very rigid because they have a vacuole filled with cell sap, and a thick cell wall, which provides structure to the plant cell. The cell membrane allows movement of things in and out cells, but in plants the thick cell wall surrounds the cell membrane and makes it difficult for plant cells to communicate with other. When cells communicate with other cells, this is called intercellular signalling.
Cells can communicate with each other by direct contact, and this is called an intercellular junction. In plant cells these intercellular junctions are called plasmodesmata (plasmodesma for a singular one). Plasmodesmata are like tiny tunnels running through the cell walls and connect the cytoplasm of two neighbouring cells. When cells communicate directly though the plasmodesma, this is called the symplastic pathway. When cells communicate through the cell wall, this is called the apoplastic pathway. Plasmodesma are only found in plant and algal cells; animal cells have something similar called the gap junction.
Plasmodesmata are only around 50-60 nanometres wide. One nanometre is a millionth of a millimetre, which means plasmodesmata are so tiny that scientists cannot study them properly using a normal microscope! Using special equipment, scientists have found that plant cells use the plasmodesmata to transport different things such as water, nutrients, hormones, proteins, and RNA which acts as a messenger for carrying instructions from DNA. Viruses can also use these tunnels to attack plant cells and spread themselves in plants! A plant can also close its plasmodesmata if it is injured, or to try and block viruses from entering. Plant cells can use plasmodesmata to send electrical signals to communicate with plant cells further away.
Scientists are still studying these special structures, and further research is needed to help us understand all the ways plants use these plasmodesmata!