Difference of the Stomatal Frequency in the Leaf Position of Ceriops decandra Leaves in Connection to Transpiration, Photosynthesis and Salt Extrusion

Karen-Lou B. Carlos; Michelle D. Doronilla; Marilyn M. Ogatia; Adrea H. RuizDepartment of Natural Sciences, College of Science, Polytechnic University if the Philippines

Sta. Mesa Manila, Philippines_____________________________________________________________________________________

ABSTRACTThe purpose of this study was to investigate the difference of stomatal frequency in the leaf position of Ceriops

decandra and its connection to the process of transpiration, photosynthesis and salt exclusion. It was observed that the leaves on the crown area of the plant have the greatest number of stomata. It was hypothesized that it was due to the great need of juvenile leaves, concentrated on the crown, to grow and expand. Thus, their large number stomata would help them to intake more CO2 needed in the process of photosynthesis. The number of stomata in the leaf surfaces affects the rate of transpiration and photosynthesis. However, Ceriops decandra, do not posses salt glands to excrete salts in the leaves unlike other mangrove species. Getting the stomatal impression, counting of the stomata and epidermal peeling were conducted to get the stomatal frequency and the characteristics of the stomata. ___________________________________________________________________________________________________

INTRODUCTIONMangroves are tree or shrubs that grow

in saline coastal habitats in tropics and subtropics. There are seventy (70) species of mangroves worldwide and they are classified into red mangroves, white mangroves, black mangroves, and mangrove palm and mangrove apple. Rhizopora, Ceriops and Brugeria are genera under the family Rhizoporaceae or the red mangroves. Genera under this family have aerial roots, which serve as prop roots for support when they come in contact with the soil. Because they are growing in salt water, they have specialized glands or ultra-filters that help them to limit their salt intake. Ceriops decandra, also known as “bataan” in Mindoro, has leathery leaves with obscure leaf veins. The leaves are of moderate size. Stomata are pores between two specialized cells called guard cells. Subsidiary cells are cells associated with guard cells and control the opening and the closing of the pores. These pores serve as exits of the water vapor from the process of transpiration and pathway of gases, like CO2, essential to the photosynthesis. Stomata are usually located on

the abaxial surface of the leaf but some species also have stomata on their adaxial surface.

This study aims to characterize the stomata of Cerios decandra, determine the difference of the stomatal frequency on the crown, lateral fluorescence and base, and the effect of the number of stomata on the process of transpiration, photosynthesis and salt exclusion.

METHODOLOGY

Sampling

The specimens, Ceriops decandra leaves, were gathered from two (2) sites in Mindoro Philippines. Codes were used to identify the origin of every specimen (e.g MC021). The first letter in the code indicates that the specimens were from Mindoro. The site where they were gathered was represented by the second letter. The next two numbers correspond to the number of the tree and the leaf position (crown, lateral fluorescence or base) was indicated by the last letter. Ten (10) leaves were selected from every code.

Stomata impression

The leaves were cleaned using cotton and ethanol. Clear nail polish was applied on the half part of the abaxial surface of the leaf. Using a clear tape, the dried nail polish was gently peeled off the leaf and taped on clear glass slides. The slides were labeled using the code the leaf corresponds. Another number was added code which indicates the leaf number.

Stomata counting

The slides with stomata impression were focused under the Low Power Objective of the microscope. The field of magnification was divided into four quadrants with the help of ocular micrometer. The counting of the stomata was facilitated using a table counter. The results were recorded.

Epidermal peeling

Ceriops decandra leaves were cut into 1 cm x 1 cm squares. It was then boiled into 10 ml copper sulfate for five (5) minutes. Five (5) mL of concentrated Hydrochloric acid was added after the set-up cooled down. It was then exposed to heat to boil for five (5) minutes. The leaf tissues were washed with water and cleansed using a soft brush. The tissues were then stained using saphranyn for one whole night. Dehydration process was conducted using different concentrations of ethanol (25%, 50%, 75% and concentrated ethanol) for five (5) minutes each. Clearing process was the next step wherein the tissues were subjected to different concentrations of chloroform ( 25%, 50%, 75% and concentrated chloroform) also for five minutes each. Using the Canada Balsm, the tissues were mounted on clean slides.

RESULTS

Ceriops decandra

Leaf Position- significant Table1.Stomates Frequency

Sum of Squares df

Mean Square F Sig.

Between Groups

1069475.117

2534737.55

819.750 .000

Within Groups

3167891.475

117 27075.996

Total 4237366.592

119

*The mean difference is significant at the 0.05 level

The table shows that there is a significant difference between the groups of the leaves.

Table2.Multiple Comparisons

(I) Leaf position (J) Leaf position significance

crown Lateral florescence 0.116

base 0.000Lateral inflorescence crown 0.116 base 0.000base crown 0.000

Lateral florescence 0.000

*The mean difference is significant at the 0.05 level Table 2 shows the significance on the

stomatal frequency between leaves of Ceriops decandra from the different leaf positions. There is no significance on the stomatal frequency between the crown and the lateral fluorescence but there is significance between the lateral fluorescence and base, and between base and crown.

Figure 1 shows the stomata of Ceriops decandra under HPO. The stomata were characterized as amphicyclocytic due to the cells, called subsidiary cells, surrounding the guard cells. The subsidiary cells formed rings which made them distinct from ordinary epidermal cells.

DISCUSSIONS

The results gathered suggest that mangrove species used, Ceriops decandra, has the greatest stomatal frequency count recorded at the crown than that of lateral fluorescence and base. Young or juvenile leaves are located at the apical part or the crown portion of the plants and mature or older leaves are concentrated on the basal part. Because juvenile leaves are still undergoing development, they have more stomata than the mature leaves. More stomata indicate fast growth.( )

The shape of the leaves of Ceriops decandra, is obovate, the leaf margin is entire. The stomata of the specimen are characterized as amphicyclocytic because it has doubled ring of five (5) or more cells each enclosing the guard cells.

Stomatal Frequancy on the Rate Transpiration

Transpiration is the evaporation of water from the aerial portions of the living plants through the stomata on the surfaces ( abaxial or/and adaxial ) of the leaves. Opening of stomata, due to different factors such as light, supply of water and temperature, increase the rate of transpiration. Thus, the more the stomata the leaf has, the higher the rate of transpiration ( ).

Stomatal frequency on the Rate of Photosynthesis

Gases needed by the plants enter and move out of the leaf through stomatal pores. Carbon dioxide (CO2), a gas necessary in the process of photosynthesis also enters via stomata. The higher the intake of CO2, due to large number stomata on a leaf, indicates the higher rate of photosynthesis.

Photosynthesis occurs in the mesophyll layer of the leaf. Mesophyll cells have chloroplast which enables them to photosynthesize. Guard cells, specialized cells that surround the stomatal pores, also have chloroplast which means they can also undergo the process of photosynthesis ( ), but in reduce rate. Mesophyll cells and guard cells are all capable to photosynthesize, thus increasing the rate of photosynthesis.

Stomatal frequency on salt exclusion

Physiologically, mangroves can tolerate a high salinity level and have mechanism to obtain fresh water despite the strong osmotic potential of sediments.. Ceriops decandra is one of red mangroves that exclude salt through its significantly impermeable roots which are

highly suberised, acting as an ultra-filtration mechanism to exclude sodium salts from the rest of the plant . It has ultra-filters in its root systems that exclude salt while extracting water from the soil (Kathiresan 2001). The exclusion of salt could make the soil salt very concentrated, thus creating strong osmotic gradient. However, vicious, polymeric substances in the sap limits flow rate and decrease transpiration. This, combined with high water-use efficiency, slows the rate of water uptake and prevents salts from accumulating in the soil surrounding the roots. This helps the mangroves, specifically Ceriops decandra, conserve water and regulate internal salt concentrations. Because of the ultra-filters on the roots of Ceriops decandra, they do not need to exclude salt through the pores on their stomata.

CONCLUSION

Therefore, the leaves from the crown have the highest stomatal frequency compared to the leaves on the lateral fluorescence.

REFERENCES

Bernard S. Meyer et.al(1975), Introduction to Plant Physiology, Litton Educ. Publishing Inc.

Bidwell et.al , Plant Physiology Second Edition, Macmillan Pub. Co.,Inc. New York

Bannisten et.al, Introduction to Physiological Plant Ecology, Blackwell Scientific Pub., Osney mead, Oxford

The Philippines Recommends for Mangrove Production and Harvesting (1991) DENR PCAARD

Devlin and Witham, Plant Physiology Fourth Edition, William Grant Press, Boston

Kathiresan and Bingham, (2001) Biology of Mangroves and Mangrove Ecosystem Vol.40:81-251