Under attack What type of specialised cells will
- Slides: 8
Under attack! • What type of specialised cells will this cow and caterpillar be eating? • How will the plant cope with the damage?
Specialised cells in plants • • • Palisade mesophyll Spongy mesophyll Epidermis (lower and upper) Guard cells stomata Phloem sieve tubes and companion cells Xylem vessels
Leaf cross section Flickr Fayette A. Reynolds M. S
Cell division to regrow • Cell division in plants usually occurs in regions called meristems, located at shoot and root tips
Cell division to regrow • Stem cells in the meristems can divide and differentiate to produce all types of plant cells at any time. • In the case of some plants the growing shoot (the apical meristem) is at ground level. So, if a cow grazes grass or a gardener picks some lettuce leaves for lunch, the meristem is unlikely to be damaged and the plant continues to grow new leaves.
Meristems at the top of the stem • If the plant grows tall, the apical meristem is at the top of the stem may be eaten or damaged by a grazing animal. • Meristems further down the stem will start to grow producing new shoots.
New discovery shows plant can seal the wound • Scientists have found cells next to the wound can replace the damaged tissue. • The healthy specialised cells adjacent don’t just divide to replace the damaged ones and fill the gap. The damage causes the cells next to the wound to revert to being totipotent stem cells and produce cells of the correct type.
• So an epidermis cell can revert to being a totipotent stem cell and produce a palisade mesophyll cell to replace the one that is damaged next to it.
