Abstract
Key message
Despite high rates of root elongation during phreatophyte establishment, once connection to groundwater has occurred and leaf area develops, seedlings demonstrate limited capacity for root elongation in response to groundwater decline.
Abstract
In a water-limited environment, rapid root elongation immediately after germination can be critical for a plant to reach deeper water sources such as a water table to avoid water deficit stress. However, once plants have accessed a water table, their continued survival may depend on their ability to adapt their root distribution to changes in the depth to a water table. In glasshouse experiments using two Banksia species with contrasting water requirements, we investigated (1) the rate of root elongation by young seedlings in the presence of a shallow water table, and (2) whole plant response to rapid water table decline using older seedlings that had established root contact with a water table. The results of the first experiment agree with the hypothesis that the facultative phreatophyte, B. attenuata, has a faster rate of root elongation than the obligate phreatophyte, B. littoralis. These differences are likely related to the contrasting habitat preferences of the two species. Older seedlings in the second experiment demonstrated a water-saving response to a declining water table, rapidly closing stomata to limit water loss. Additionally, roots did not elongate to follow the water table and plants were quickly disconnected from the saturated zone. For the two phreatophytic Banksia species, the capacity for rapid root growth by young seedlings did not translate to an ability for established seedlings to adapt their root distribution to survive rapid water table decline.
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Author contribution statement
W. Stock, R. Froend and C. Canham conceived and designed the experiments; C. Canham performed the experiments and analysed the data; C. Canham, R. Froend and W. Stock wrote the paper.
Acknowledgments
The authors wish to acknowledge the support of the Water Corporation of Western Australia and the Australian Research Council.
Conflict of interest
This research was financially supported by an Australian Postgraduate Award associated with Australian Research Council Linkage Project LP0669240, and the Water Corporation of Western Australia. The authors declare they have no further conflict of interest.
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Communicated by H. Rennenberg.
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Canham, C.A., Froend, R.H. & Stock, W.D. Rapid root elongation by phreatophyte seedlings does not imply tolerance of water table decline. Trees 29, 815–824 (2015). https://doi.org/10.1007/s00468-015-1161-z
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DOI: https://doi.org/10.1007/s00468-015-1161-z