ASHRAF, Maria and Hidayat, Jafron Wasiq and Muhammad, Fuad (2023) COMPARISON OF SALINITY TOLERANCE BETWEEN AVICENNIA MARINA AND RHIZOPHOR MUCRONATA KARACHI COAST, PAKISTAN. Masters thesis, UNIVERSITAS DIPONEGORO.

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Abstract

Mangrove propagule size variation is an important factor in their survival. Propagules size variation of Avicennia marina and Rhizophora mucronata were collected from the Indus delta and has been grown in the polythene bags of 5x10 inches filled with silty soil from field nursery of “Institute of environmental studies. Different salinity and nutrient treatments were given to propagules 25% and 50% seawater and Hoagland solution. Seedlings were experimentally grown for 6 months and observed the forestry parameters i.e., initial length of plants was observed in 50% seawater and declined with increasing salinity. Fresh water has also been given thrice a week to wash out the excess salt concentration. Optimum salinity in the Rhizophora species was 50% seawater, Rhizophora species class 1 show the Plant height of (1.057 ± 18.962 cm) and class 2 show the least Plant height (15.304 ± 0.995 cm) show maximum growth due to the given concentration of 50% sea water. Propagules of A. marina often show growth stimulation at low salinity 25% seawater and then a decline in growth with further increases in salinity. Avicennia marina class 1 show plant height (36.45 ± 0.61 cm) and class 2 shows plant height (27.66 ± 0.23 cm). Higher stomatal conductance was noted in R. mucronata, followed by A. marina. Sodium and chloride ions increased with the increase in salinity and this accumulation was much higher in A. marina. It was observed that medium and large size propagules show better results in artificial greenhouse environment as compared to small size of propagules.
A. marina, it is the most salt resistant mangrove species; and thus, its dominance is quite logical. A. marina accumulated the highest concentrations of ions followed by R. mucronata and Avicennia marina has the ability to regulate salt content by secreting it through the glands, while R. mucronata have the ability to exclude salts via root ultrafiltration. A. marina shows a positive requirement for high chloride levels for photosynthetic electron transport around photosystem. There is some evidence from the present results that root growth in this species is particularly responsive to an increase in salinity in the bathing medium. It may therefore be premature to conclude that the stimulation of halophytes growth by increased levels of salt in the growth medium is primarily due to increases in turgor pressure and extension growth the decline in growth of the plant and the corresponding decline in the root respiration rate at salinities greater than 25% seawater indicates that A. marina seedlings are not well adapted to conditions of salinity approaching that of seawater, in terms of optimal growth, although they are capable of tolerating conditions of very high salinity.

Keywords: Avicennia marina, Rhizophora mucronata, propagules, salinity, stomal conductance, Hoagland solution, Seawater

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