ABSTRACT
The present study contributes information about the environmental factors controlling the distribution, variation in standing crop phytomass and chemical compositional change of Ludwigia stolonifera. Also, treatment with cattle manure, as source of organic waste, was made to evaluate the responce of the plant to the environmental pollution. The sandy textured bottom sediments of Ludwigia habitat at Damira irrigating canal had higher percentages of organic carbon and total soluble salts in spring than in the other seasons while the overlying water was characterized by low total soluble salts. The phytomass and assimilating surface area were increased in spring and summer months and appeared to decline in winter. The phytochemical constituents were highly concentrated during August. As common in hydrophyte, the plant organs of L. stolonifera are characterized by abundance of aerenchyma, absence of cork cells and reduction of vascular tissues. Addition of cattle manure to the aquatic habitat of Ludwigia plant resulted in an increase of organic carbon, salinity, chloronity and in a decrease of pH value of hydrosoil and water. Heavy metals accumulation showed considerable increase due to application of cattle manure and this appeared to be a reflection to the increased concentrations of these metals in the environment.
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DOI: 10.3923/pjbs.2007.2025.2038
URL: https://scialert.net/abstract/?doi=pjbs.2007.2025.2038
INTRODUCTION
The total length of irrigation and drainage canals in the Egyptian Nile System, is approximately 47000 km. About 87% of the irrigating canals and 74% of the drains are infested with most types of aquatic weeds. This invasion could be explained due to different aspects. The degree of infestation is usually affected by the environmental factors including depth of water, physico-chemical water quality, water currents, sediments type and atmospheric temperature (Abo El-Lil, 1987; Wang et al., 1997).
During the last few years, macrohydrophytes have received great attention, not only for the magnitude of problems caused by them in the management of water resources, but also for the promise they hold as a new resource, for such diverse uses as animal fodder, compost, paper, energy (biogas) and above all control of pollution (Gopal, 1987; Pieterse and Murphy, 1990).
The biomass and mineral composition of the macrohydrophytes in relation to water quality in the Nile Delta canals would be very useful in development of any kind of wetland management program (Westlake, 1975). Also Ecological factors that may counteract the existence and vital activities of harmful aquatic weeds must be investigated, enhanced and multiplied.
L. stolinifera is widespread aquatic weed in canals and drains crossing the cultivated lands in the Nile Delta (Tackholm, 1974; Boulos, 2000). As many floating macrohydrophytes, Ludwigia plant tends to aggregate and is frequently so dense as to block the whole water way. This weed can spread out from the bank for a considerable distance on account of the floats, which support the plant. It is very easily distributed on account of its seeds being numerous and the fact that small pieces of the plant can root themselves in the mud when broken from the stem (Abo El-Lil, 1987; Khattab and El Gharably, 1990). Many studies evaluate L. stolonifira (water primrose) as economic plant, for example: It is used for removing a common agricultural chemicals and contaminants from water and helping to improve drinking water quality, where it took up atrazin from water (Larson, 1999). Because of the pretty and showy flowers, it is being sold as ornamental species (Zardini et al., 1991).
The ultimate goal of this study is to give Knowledge about the relation between the habitat conditions and the changes of growth, metabolites content and mineral composition as well as anatomical features of L. stolonifera plant, which inhabits many sites at El-Dakahlia province. Also, experimental study was preformed to evaluate the effect of cattle manure as organic pollutant on growth of the plant and accumulation of heavy metals by its organs.
MATERIALS AND METHODS
The site selected for the present study is Damira irrigation canal, which is located at 14 km to the north of Talkha and 6 km to the south of Bilgas (Fig. 1). Its width is about 4 m and water depth rarely exceed 1 m. It is characterized by great masses of L. stolonifera (Fig. 2).
The monthly mean of the climatic particulars of El-Dakahlia province during the period 1980-2000 were obtained from the Department of Meteorological, Cairo.
Hydrosoil and subsurface water samples were collected monthly from the study area for a period of one year beginning from February 2000 to January 2001 and analyzed for estimation of their physical and chemical characteristics according to the methods described by Jackson (1962) and American Public Health Association (1985).
The plant samples for growth measurements were collected monthly from naturally growing Ludwigia plants using quadrate 1×1 m2 (Grieg-Smith, 1982). Other plant samples were collected for the phytochemical analyses following the methods recommended by Egyptian Pharmacopoeia (1953) and Handel (1968).
The floristic components of Ludwigia community type were recorded in a series of representative stands. The list of species was made including phonological aspect, cover-abundance and presence estimates (Kent and Coker, 1992).
Data of the successive estimations of the biomass and assimilating surface area were applied to assess growth characteristics according to the classical growth analysis which was described by Hunt (1978) and Coombs and Hall (1982).
Fig. 1: | Location map of the studies site |
Fig. 2: | General view of L. stolonifera stand at Damira irrigation canal |
For anatomical investigation, thin sections of aerial stem, offset, leaf and root were prepared according to Peacock and Bradbury (1973).
Organic pollutant experiment: Twenty Ludwigia plants representing variable sizes were collected from Damira irrigation canal at mid-June 2001 and transplanted in a ditch (25 m long, 2.5 m width and 47 cm water depth) located at 1 km south of Damira village. At the start of the experiment, other five plants were collected for measuring the growth parameters and quantify the concentrations of the heavy metals in the different plant organs before application of the pollutant. hydrosoil and water samples were collected from the ditch and analyzed (control). Cattle manure was spread on water surface of the ditch at a ratio of 5% (14.68 kg/29375 L water). Five plants were harvested 60, 90 and 105 days after application of the cattle manure. The plants were separated into stems, leaves, floral buds and roots. Their dry weights were detected. Estimation of heavy metals content of both treated and untreated plants was preformed using the procedures described by Allen et al. (1986). At each harvesting time, hydrosoil and subsurface water samples were taken and analyzed.
RESULTS AND DISCUSSION
The climatic data of the area in which the plant abundantly grows would be of ecological importance. It is obvious from the data presented in (Table 1) that L. stolonifera is subjected to wide seasonal fluctuations of air temperature (6.8°C in January-34.5°C in July), relative humidity (53% in May-71% in November) and evaporative power of air (2 mm/day in January-5.5 mm/day in June). It may be concluded from the foregoing data that the luxuriant growth of Ludwigia plant is associated with mild atmospheric conditions caused by low relative humidity and high evaporating power at late spring- early autumn.
Regarding the bottom sediments, data in Table 2 revealed that all soil samples are sandy textured with a sand fraction up to 98 %. The silt particles ranged from 1-9%, whereas clay particles were absent. Porosity attained moderate values allover the year (46.4-57.6%). CaCO3 content was generally low and elevated to 9% in August and October. Organic carbon content (0.8-3.8%) and Total Soluble Salts (TSS) (0.13-0.34%) were relatively higher in spring than in other seasons. Chlorides content was very low (0.01-0.05%), soluble carbonates were absent while sulphates (0.025-0.164%) and bicarbonates (0.031-0.183%) seemed to be the major constituents of soluble salts. Cations determination proved that, among the macroelements Na+ and Ca2+ showed relatively high concentrations (13.8-17.1 and 7.6-12.0 mg/100 g dry soil, respectively), while concentrations of K+ and Mg2+ were very low (1.1-1.6 and 0.8-1.26 mg/100 g dry soil, respectively). The microelements contents were relatively low and each fluctuated within a narrow range. The soil reaction appeared all the time towards the alkaline side (pH: 7.91-8.87).
Analysis of water (Table 3) showed that the water quality was characterized by high organic carbon and low total soluble salts, Cl‾, SO4‾‾ and HCO3‾ during summer months. There were high concentrations of Na+,Ca2+, K+ and Mg2+ ions, which are important structural components of plant tissues and Mg2+ is an essential constituent of chlorophyll. Pb2+ and Cd2+ have low concentrations while Cu2+, Fe3+ and Mn2+ concentrations could be considered trace. Water reaction was alkaline allover the year.
On the basis of the above results, it is worthy to note that the chemical components of the overlying water change seasonally rather than spatially. The reverse is nearly the case with the chemical components of the underlying soil. Ludwigia plant is known to have low tolerance to salinity and chloronity and usually forms extensive thickets that abound on irrigation canals with underlying soil of aeolian sand and alluvial fine sediments that become enriched with organic matter produced from decayed offsets and fallen leaves.
Table 1: | Climatic data of El-Dakahlia District during the period taken from Cairo Meteorological Department |
Table 2: | Physical and chemical analysis of soil samples supporting Ludwigia stolonifera at Damira irrigation canal |
Table 3: | Analysis of water samples supporting Ludwigia stolonifera at Damira irrigation Canal |
It is evident from (Table 4) that this aquatic plant community includes limited number of associates, 12 perennials and 9 annuals. These associates have low presence estimates (5-40%) with exception of Echinochloa stagnina and Eichhornia crassipes with presence estimates of 65 and 60 %, respectively. L. stolonifera being the dominant (p = 100%), is consistently the most abundant. Its growth provides the main bulk of the vegetation cover. The total plant cover ranged from 70 to 100%.
The results obtained from the monthly changes in the standing crop phytomass and assimilating surface area (Table 5 and Fig. 3 and 4) revealed that the vegetative yield of this plant is observed all the year round with prosperous growth in spring and summer months, then declined in winter. Generally, floating hydrophytes show poor growth in winter. Such seasonal fluctuation in the growth may be attributed to temperature changes. These findings are in accordance with Pulish (1985) and Abo El Lil (1987). Regarding the aquatic weeds as energy and biomass resources, El-Habibi et al. (1988) pointed out that the annual biomass production of free-floating hydrophytes was greater (3-10 folds) than those of both emergent and submerged ones.
The density of L. stolonifera appeared to increase gradually from 98 stem m2 in January to 174 stem m2 in September. The maximum height of the stem was 78.5 cm in September. Again, the highest number of leaves/stem (26.6) was recorded in September and the lowest leaf nomber/stem (16.1) was in January. Several studies confirmed this trend (Ho, 1979; Dinka, 1986). Concerning the influence of soil and water on growth of L. stolonifera, it is concluded that the biomass accumulation and assimilating surface area tended to be enhanced by decrease in salinity and pH range of 8.22-8.95.
Examining of the growth characteristics showed that the monthly changes of Relative Growth Rate (RGR), Relative Assimilating Surface Growth Rate (RASGR) and Net Assimilating Rate (NAR) were more or less similar. Their changes correspond to each other as demonstrated in (Fig. 5-10). High RGR was attained during the early stages of growth but at maturity the RGR and RASGR appeared to decline. The Leaf Weight Rate (LWR), Leaf Area Rate (LAR) and Specific leaf area (Spec. LA) were generally high. This may be related to the high rate of photosynthesis. These results are in accordance with that obtained by Sale et al. (1985).
Dealing with the phytochemical investigation of Ludwigia, the results in Table 6 revealed that the highest values of acid-insoluble ash, total lipids, total nitrogen, sucrose and total soluble sugars were observed in the leaves, while those of total ash, water-soluble ash, crude fiber and total carbohydrates were met within the stems. Most of these constituents appeared to predominate during summer (August). The pattern of changes in reducing sugars and sucrose as well as in total carbohydrates appeared to be closely correlated with plant organs and stage of development and seems to coincide with the increases in all growth parameters of the plant. It is perhaps relevant to mention here that the photosynthetic efficiency was increased leading to enhancement of biosynthesis of carbohydrates, which are utilized in the growth of the plant. The present results seem to be in good agreement with those obtained by Pomogyi et al. (1984) and Serag et al. (1999).
Concerning the minerals content, it is clear from Table 7 that, in all seasons, Ludwigia leaves accumulate amounts of K+ and Ca2+ higher than those accumulated by stems and roots, whereas Na+ appeared to exhibit the highest values in root. Mg2+ content showed an irregular pattern of monthly variation. With respect to Fe3+ content, the roots accumulated the highest amount of this element. Cu2+ content of the leaves appeared to be less than that of the other plant parts. It maintained the highest value during March and the lowest value during October.
Regarding the anatomy of aerial stem and offset of L. stolonifira (Fig. 11 and 12), there is a single layered epidermis composed of thin walled cells that possessed a thin cuticular covering. Cortex is highly developed with a distinctive middle region made of aerenchymatous cells enclosing well-developed intercellular spaces. The vascular tissues are poorly developed, forming continuous cylinder traversed by narrow rays. The xylem vessels are moderately small and thicker walled in offset than in aerial stem. Sclerenchyma and cork cells appeared to be generally absent. The leaf is dorsiventral with distinct palisade and spongy tissues (Fig. 13). The palisade tissue appeared to enclose large spaces while the spongy tissue is mainly aerenchymatous. Raphides are commonly found in the spongy cells. The root is characterized by lacking of cuticle and root hairs from the epidermis. Cortex is composed of aerenchyma cells with large air spaces separated by one-cell-thick septa. The vascular system is represented by simple stellar structure (Fig. 14).
Organic pollution experiment: With regard to changes of hydrosoil characters, data in Table 8 revealed that the addition of cattle manure to the aquatic habitat resulted in an increase of organic carbon, salinity, chlorides and some cations contents. In accord with this finding,
Table 4: | Monthly variation in the floristic composition of permanent stand dominated by Ludwigia stolonifera at Damira irrigation Canal |
gr: Green, fl: Flowering, fr: Fruiting, d: Dry and P: Presence |
Table 5: | Monthly variation in vegetative yield of L. stolonifera growing at Damira canal |
H = Height of stems, L = Leaf number per stem and N = Node number per stem |
Fig. 3: | Monthly variation in biomass content of L. stolonifera |
Fig. 4: | Monthly variation in assimilating surface area of L. stolonifera |
Fig. 5: | Monthly variation in relative growth rate of L. stolonifera |
Fig. 6: | Monthly variation in relative assimilating surface growth rate of L. stolonifera |
Fig. 7: | Monthly variation in net assimilating rate of L. stolonifera |
Fig. 8: | Monthly variation in leaf area ratio of L. stolonifera |
Fig. 9: | Monthly variation in leaf weight ratio of L. stolonifera |
Fig. 10: | Monthly variation in specific leaf area of L. stolonifera |
Fig. 11: | Light microscopy of transverse section of stem of L. stolonifera |
Fig. 12: | Light microscopy of transverse section of offset of L. stolonifera |
Fig. 13: | Light microscopy of transverse section of leaf of L. stolonifera |
Fig. 14: | Light microscopy of transverse section of root of L. stolonifera |
Table 6: | Analysis of Ludwigia stolonifera plants growing at Damira Canal |
Table 7: | Monthly variation in elements content of Ludwigia stolonifera plant growing at Damira Canal |
Table 8: | Periodical changes in soil samples supporting Ludwigia stolonifera during the experiment of cattle manure effect |
Table 9: | Periodical changes in water samples supporting Ludwigia stolonifera during the experiments of cattle manure effect |
Ismail et al. (1996) had concluded that cattle manure was the richest material to induce total amounts of Pb2+, K+, Fe and Mn2+ in comparison with the other organic wastes sources (sewage sludge and town refuse). Concerning the changes of water characters, it might be concluded from the results in Table 9 pH were slightly increased. At the end of the experiment, the % of total soluble salts, Cl‾, SO‾‾4 and HCO‾3 reached their highest values. It is interesting to note that, soluble carbonates were detected in water after treating with cattle manure. The highest values of Na+, Mg2+, Pb2+ and Cd2+ (10.8, 2.3, 0.07 and 0.08 mg L‾1, respectively) were obtained at the third harvesting period. The results obtained from vegetative growth measurements (Table 10) showed that cattle manure was able to elevate the vegetative growth at all harvesting periods compared to control plants.
Table 10: | Periodical changes in vegetative yield of L. stolonifera during the experiment of cattle manure effect |
Table 11: | Periodical changes in heavy metals content of L. stolonifera during the experiment of cattle manure effect |
Concerning the total biomass and the total assimilating surface area, both were increased approximately to 6 and 12 folds, respectively at the first harvesting period and to 15 and 30 folds, respectively at the third harvesting period. As regards the heavy metals accumulation by L. stolonifera, it is obvious from (Table 11) that the concentration of most metals showed progressive increases due to application of cattle manure. Cyerman and Kempers (2001) reported that, the increased concentrations of heavy metals in plants seem to be a reflection of the increased concentrations of these metals in the environment. As evident from the experimental results, all tested heavy metals were much higher in the roots than in stems, leaves and floral buds. Mn2+ was recorded with detectable values in the floral buds only. Cd2+ was detected as traces in the different plant organs. These results are in agreement with those obtained by Sprenger and Mclntosh (1989) and Ali and Soltan (1999).
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