Sauromatum venosum - 9 months on - An update of Ruperts progress and info about senescence in Aroids

Описание: SENESCENCE IN AROIDS

PAPERS

Living to Die and Dying to Live: The Survival Strategy behind Leaf Senescence1

https://www.ncbi.nlm.nih.gov/pmc/arti...


Relationship between nitrogen resorption and leaf size in the aroid vine Rhodospatha oblongata (Araceae)
https://www.publish.csiro.au/bt/bt16231

Structural and mechanical peculiarities of the petioles of giant leaves of Amorphophallus (Araceae)
https://pubmed.ncbi.nlm.nih.gov/21652...

Tuber, rhizome and bulb development and Ageing and senescence
https://www.slideshare.net/slideshow/...

LEAF SENESCENECE IN AROIDS

Leaf senescence in aroids, as in other plants, refers to the natural process of aging and eventual death of a leaf. This is a highly regulated biological process that allows plants to conserve resources, recycle nutrients, and prepare for seasonal changes or environmental stresses. In aroids, this process can be particularly noticeable as they are often grown for their attractive foliage.
Here’s a breakdown of leaf senescence in aroids:

1. What is Leaf Senescence?

Leaf senescence is the final stage in a leaf’s lifecycle, which results in the breakdown of cellular components, the withdrawal of nutrients from the leaf, and eventually the death of the leaf. It is distinct from leaf abscission (where the leaf detaches from the plant) but often leads to it. In aroids, senescence typically occurs when:
The leaf has fulfilled its role in photosynthesis.
The plant is preparing for dormancy (such as in tuberous aroids like Amorphophallus).
The plant is under stress, such as drought, nutrient deficiency, or changes in temperature.

2. Triggers for Senescence in Aroids:

Senescence in aroids can be triggered by several internal and external factors:
Age: The most common reason for leaf senescence is simply the leaf’s age. Older leaves will senesce after new ones have developed.
Seasonal Changes: In species that go through dormancy (such as Amorphophallus or Gorgonidium), seasonal changes in temperature or moisture levels trigger the process. As the plant prepares for dormancy, older leaves senesce to conserve energy for the underground tuber.
Environmental Stress: Conditions such as drought, excessive sunlight, or nutrient deficiency can accelerate leaf senescence. When the plant senses these stressors, it may “sacrifice” older leaves to redirect energy and resources to younger parts.
Hormonal Regulation: Senescence is regulated by plant hormones, particularly ethylene, abscisic acid, and cytokinin. Ethylene promotes senescence, while cytokinin can delay it by promoting cell division and leaf longevity. Stress hormones like abscisic acid can speed up senescence.

3. Visible Signs of Senescence in Aroids:
Yellowing of Leaves: The breakdown of chlorophyll causes the leaf to turn yellow (chlorosis), which is the most common sign of senescence in aroids.
Drooping or Wilting: As the leaf cells begin to lose turgor pressure, the leaf may start to droop.
Browning and Drying: After the yellowing phase, the leaf may turn brown as more cells die and dry out, eventually becoming brittle.
Leaf Abscission: In some aroids, after the leaf has fully senesced, it may be shed by the plant. The abscission process occurs at the petiole, where the plant forms a separation layer, and the dead leaf drops off.

In summary, leaf senescence in aroids is a natural process that allows these plants to optimize energy use and survive seasonal changes or stress. Understanding this process can help growers maintain healthy plants by recognizing when it is normal and when it may indicate a care issue.

GLOSSARY

apoptosis - the death of cells which occurs as a normal and controlled part of an organism's growth or development
Also called programmed cell death
Programmed Cell death - see apoptosis

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