Senescence of plant tissues is a physiologically synchronized process that enables an evergreen or a perennial plant to retrieve, recycle and remobilize nutrients from elder to younger tissues or upcoming seeds. The succulent perennial halophyte S. quinqueflora utilizes this process to discard excess salt being accumulated in outer tissues of their leafy stems. The exact mechanism for salt shedding in this plant, however, remains elusive. In this work we show that the plant develops two distinct types of tissues - an endodermis-like layer (suberized layer, ED), and an additional internal photosynthetic layer (IP) - to enable this process. Their potential roles toward salt-coping strategy were investigated in this study. We show that elevated salinity leads to an accelerated development of the ED, and that its development strongly affected ion partitioning between outer (senescent) and inner (non-senescent) tissues. A positive correlation between the ratio of ED to a bead diameter and the outer to inner concentration of Na+ was observed. These ratios were highest in older (basipetally-located) beads and progressively decreased towards the tip. Furthermore, the Na+/ K+ ratio in inner tissues of bottom beads at highest salinity treatments (800 and 1000 mM NaCl) that showed clear senescence symptoms was ∼1.0, indicative of complete separation of the outer and inner tissues at late developmental stage due to the fully suberized ED multilayer. A dual-sources: dual-sinks model explaining the role of the IP layer in plant adaptation to salinity is presented.

Item Type:	Refereed Article
Keywords:	salinity; sodium; suberization; succulence;
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Other plant production and plant primary products
Objective Field:	Other plant production and plant primary products not elsewhere classified
UTAS Author:	Ahmed, H (Dr Hassan Ahmed)
UTAS Author:	Shabala, S (Professor Sergey Shabala)
UTAS Author:	Goemann, K (Dr Karsten Goemann)
UTAS Author:	Shabala, SI (Associate Professor Lana Shabala)
ID Code:	155139
Year Published:	2022
Deposited By:	Agriculture and Food Systems
Deposited On:	2023-01-30
Last Modified:	2023-03-16
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