Abscission and senescence are two subsequent processes that remove superfluous components from the plant body. Abscission is a form of self-pruning that minimises water and nutrient loss from plants while also protecting them from bacterial and fungal infestation. On the other hand, senescence is the result of age-related metabolic and physiological processes.
Senescence
Senescence has been characterised as the decline of an organism’s or organ’s functional life. While meristems do not suffer senescence and are thus potentially eternal, all of the cells produced from them age and eventually die. Senescence occurs in leaves, flowers, fruits, stems, and roots, but it frequently happens in various organs at different times.
In many perennial herbs, such as alfalfa, the entire above-ground system dies each year, but the crown and root systems stay relatively healthy. The leaves of deciduous woody perennials die, but most of the root and stem tissue remains viable. Another senescence pattern is observed in a number of herbaceous annual species, including beans, tomatoes, and cereal grains.
There is increasing senescence of the leaves as they age, followed by the death of the stem and roots following flowering. Senescence; Catskill Mountain, New York; The breakdown of chlorophyll reveals yellow, red, and orange light-gathering pigments.
Senescence, it is argued, is caused by a changed hormone balance, which inhibits genes from continuing to code for the same enzymes as they did when the cells were younger. Senescence, when viewed in this light, can be considered as the final stage of differentiation that occurs continuously from juvenility to death. It is the climax of the programme of morphogenetic information.
Types of Senescence
Senescence can be classified into the following categories according to their role in a plant’s ageing process.
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Senescence occurs in monocarpic plants, such as rice, wheat, mustard, cabbage, and bamboo, that produce flowers and fruits only once during their entire lives. It kills the entire plant; the plant dies after flowering and fruiting.
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Senescence of the shoots happens in certain perennial plants that have underground components such as bulbs, tubers, and rhizomes. After flowering, the plant that remains above ground dies, but the underground portion persists and produces new shoots the following season, e.g., banana, ginger, gladiolus, etc.
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Sequential senescence occurs in the majority of perennial plants. The tips of the main shoot and surrounding branches continue to grow and produce new bubs and leaves, but the older leaves and lateral components, such as old branches, die, e.g., Pinus, Eucalyptus.
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Simultaneous or synchronous senescence: This type of senescence occurs in deciduous trees such as the elm and maple. In the autumn, trees drop their leaves and regenerate new ones in the spring.
Abscission
Several plant organs are lost shortly after senescence occurs. This process is best understood in terms of the physiology of leaves, flowers, and fruits. Flowers last between three and four hours in Hibiscus trionum and Calandrinia compressa and three to four months in Phalaenopsis schilleriana. Leaves, on the other hand, have a longer lifespan.
The needles of the majority of herbaceous annuals are never shed and remain intact for the duration of the plant, those of deciduous woody dicotyledons remain intact for one growing season, and those of certain gymnosperms remain intact for approximately one year to seven or eight years, depending on the species and growth conditions.
The majority of fruits perish during the season in which they are produced. Abscission is delayed while the organ remains physiologically functioning and occurs when normal metabolic processes are completed or are disrupted by injury or disease. Leaf abscission is typically triggered by the younger leaves above, and one of the chemicals responsible for this is auxin.
Abscisic acid induces leaf abscission in a variety of plants. Acid and the other abscisins appear to play a significant role in the loss of leaves, fruit, and flowers. Abscission is beneficial to plants in a variety of ways. Abscission of the damaged organ is frequently caused by injury or disease. Thus, the plant eliminates a redundant component or a potential infection source.
Difference Between Abscission and Senescence
Abscission is the natural process by which plant parts detach from the parent plant, whereas senescence is the biological process by which cells enter a stable growth arrest and experience other phenotypic changes. This is the critical distinction between abscission and senescence. Abscission is critical because it enables the removal of senescent or physiologically damaged organs and the efficient dissemination of seeds. Senescence is necessary for plant fitness and survival.
Similarities Between Abscission and Senescence
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Plants undergo two distinct processes: abscission and senescence.
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Abscission and senescence are processes that occur in plants or plant components.
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Abscission enables the parent plant to shed senescent or physiologically damaged parts.
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Both processes are facilitated by plant hormones.
Conclusion
Abscission is the process by which plant components such as flowers, fruits, and leaves naturally separate from the parent plant. Senescence is a state of biological aging in which cells cease to divide and enter a cell cycle arrest phase. As so, this is the critical distinction between abscission and senescence. Abscission is critical for plants because it allows them to eliminate senescent or physiologically damaged plant sections. Senescence is necessary for the plant’s existence and the survival of subsequent generations.