Primary growth in plants is growth that takes place from the tips of roots or shoots. It leads to lengthening of roots and stems and sets the stage for organ formation. It is distinguished from secondary growth that leads to widening. Plant growth takes place in well defined plant locations. Specifically, the cell division and differentiation needed for growth occurs in specialized structures called meristems.[1][2] These consist of undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants. These cells continue to divide until they differentiate and then lose the ability to divide. Thus, the meristems produce all the cells used for plant growth and function.[3]
At the tip of each stem and root, an apical meristem adds cells to their length, resulting in the elongation of both. Examples of primary growth are the rapid lengthening growth of seedlings after they emerge from the soil and the penetration of roots deep into the soil.[4] Furthermore, all plant organs arise ultimately from cell divisions in the apical meristems, followed by cell expansion and differentiation.[1]
In contrast, a growth process that involves thickening of stems takes place within lateral meristems that are located throughout the length of the stems. The lateral meristems of larger plants also extend into the roots. This thickening is secondary growth and is needed to give mechanical support and stability to the plant.[4]
The functions of a plant's growing tips – its apical (or primary) meristems – include: lengthening through cell division and elongation; organising the development of leaves along the stem; creating platforms for the eventual development of branches along the stem;[4] laying the groundwork for organ formation by providing a stock of undifferentiated or incompletely differentiated cells[5] that later develop into fully differentiated cells, thereby ultimately allowing the "spatial deployment off both arial and underground organs."[1]
- ^ a b c Baucher, Marie; AlmJaziri, Mondher; Vandeputte, Olivier. "From primary to secondary growth: origin and development of the vascular system". academic.oup.com. Retrieved 2023-03-18.
- ^ Tognetti, Vanesa B.; Bielach, Agnieszka; Hrtyan, Mónika (October 2017). "Redox regulation at the site of primary growth: auxin, cytokinin and ROS crosstalk: Apical meristems plasticity in response to stress". Plant, Cell & Environment. 40 (11): 2586–2605. doi:10.1111/pce.13021. PMID 28708264.
- ^ Gross-Hardt R, Laux T. Stem cell regulation in the shoot meristem. J Cell Sci. 2003 May 1;116(Pt 9):1659-66. doi: 10.1242/jcs.00406. PMID: 12665547.
- ^ a b c Capon, Brian (2015). Botany for Gardeners (7th printing ed.). Portland: Timber Press. pp. 23–26, 159–160. ISBN 978-1-60469-095-8.
- ^ "Plant Development II: Primary and Secondary Growth | Organismal Biology". organismalbio.biosci.gatech.edu. Retrieved 2023-03-18.