Influence of two different forms of nitrogen on growth and physiological aspects of water-cultured seedlings of Rhizophora apiculata was studied. Of the two forms of nitrogen supplied to the growth medium, ammonium nitrogen was better than nitrate nitrogen by exhibiting increased dry matter production, shoot length, leaf area and also enhanced the contents of carotenoids, chlorophylls and their presence in photosystems and light harvesting protein complex

Kathiresan, K.

Moorthy, P.

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Pakistan Journal of Marine Sciences, Vol.4(2), 133-137, 1995 
INFLUENCE OF NITROGEN SALTS ON GROWTH AND 
PHYSIOLOGICAL RESPONSES OF RHIZOPHORA APICULATA 
BLUME IN NON-AERATED WATER CULTURE 
P. Mom·tb.y and K. Katb.iresan 
Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai, 
Tamil Nadu 608 502, India. 
ABSTRACT: Influence of two different fonns of nitrogen on growth and physiological aspects of water-cultured 
seedlings of Rhizophora apiculata was studied. Of the two forms of nitrogen supplied to the growth medium, 
ammonium nitrogen was better than nitrate nitrogen by exhibiting increased dry matter production, shoot length, 
leaf area and also enhanced the contents of carotenoids, chlorophylls and their presence in photosystems and light 
harvesting protein complex. 
KEY WORDS: Ammonium - mangrove - nitrate - photosynthesis - Rhizophora apiculata. 
INTRODUCTION 
Nitrogen is an important nutrient limiting the growth of halophytes in intertidal 
areas (Tyler, 1967; Stewart et al., 1979). Application of nitrogenous chemicals has 
been reported to increase the biomass of marshy vegetation (Tyler, 1967; Vali.ela and 
Teal, 1974; Sullivan and Daiber, 1974; Bromme et al., 1975; Naidoo, 1987). These 
studies imply the inadequate availability of specific forms of nitrogen to the plants 
for better assimilation and growth. The evidence reporting the specific forms of 
nitrogen utilised by. the halophytes, is conflicting. Tyler (1967) showed increased 
growth response of seagrass meadows to ammonium chloride treatment, but not to 
sodium nitrate and considered that, these species may require ammonium as a source 
of nitrogen (N). But, Boto et al. (1985) contradicted that nitrate is the preferred source 
of N for the enhanced growth of Avicennia seedlings; and not the ammonium N. The 
present study has been made to find out the "Physiologically active" form of nitrogen 
for the growth in seedlings of Rhizophora apiculata, a predominant mangrove species 
in the study area. 
MATERIALS AND METHODS 
Propagules of R. apiculata Blume (26±2 em in length) were coHected from 
Pichavaram mangroves (11 °27' N; 79° 4 7' E) at southeast coast oflndia, during August 
1992. The propagules were introduced into four litre plastic containers having 
Hoagland and Arnon (1950) nutrient solution with an optimal salinity of 15 g r 1. Iron 
was supplied as ethylenediamine tetra acetic acid at 1 mg r 1. The propagules were 
subjected to two different forms of N at the time of first exposure into nutrient 
solutions. Liquid culture was used since the plants absorb nutrients effectively from 
solution than soil (IPCS, 1992). 
134 Pakistan Journal of Marine Sciences, Vol.4(2),1995. 
NITROGEN TREATMENT 
Nitrogen was supplied as NH4Cl or NaN03 at different concentrations ofO, 5, 10, 
20, 30, 40, 50, 100, 150, 200 and 250 mg r 1. NaG content of treatments were 
maintained at a concentration of 15 g r 1 which was found optimal salinity for 
propagules of R. apiculata (Kathiresan and Thangam, 1990). Propagules were 
exposed to nitrogen treatments for eight days and control propagules had to rely 
entirely on internal nitrogen for growth. After the exposure, plants were reintroduced 
into nutrient medium devoid of any nitrogen. Nutrient solutions were replenished 
once in seven days. A completely randomised block of 22 treatments with five 
replicates each was maintained. Experimental set up was incubated at a temperature 
of 25±2°C with a light intensity of 330 jlmol m-2s-1. After 90 days, the plants were 
analysed for dry matter accumulation, plant height, leaf area using Li-Cor leaf area 
meter 3100 (USA), tissue nitrate content (Cataldo et al., 1975), leaf in vivo nitrate 
reductase activity (NRA) (Jaworski, 1971), N03 utilisation efficiency as the ratio 
between NRA and N03, chlorophylls (Arnon, 1949) and their fractions in 
photosystems I and II and light harvesting complex (LHC) (Krivosheeva et al., 1991) 
and carotenoids of chloroplast (Ridley, 1977). The data are presented as mean and 
different treatments were statistically analysed and the least significant difference 
(LSD) at 5% level of probability is given. 
RESULTS AND DISCUSSION 
Both forms of nitrogen had significant effect on dry matter production. In general, 
shoot dry matter was greater than root in both the treatments. NH4Cl increased the 
' 1 
shoot dry matter by 133% and root by 68% at 100 mg r . NaN03 enhanced the shoot 
dry matter by 198% and decreased the root dry matter by 25% at 100 mg r 1 (Fig.;1). 
However, higher concentrations reduced the dry matter production whereas lower 
concentrations had no significant effect. The increase in dry matter production in 
optimal concentrations of both treatments reveals the efficiency of R. apiculata to 
assimilate both forms of nitrogen. However, ammonium-N was more efficiently 
utilised by this species than nitrate N by increasing the growth of both root and shoot 
systems. 
Root length was recorded a maximum of 45% in N03 treatment at 100 mg r 1 and 
27% in NH4 treatment at 40 mg r 1. The increased root length was not found associated 
with root dry matter accumulation which may be attributed to the lack of correlation 
between the growth and thickness of root Shoot length was promoted by 78% in 20 
mg r 1 treatment of NH4 and 100% in N03 at 100 mg r 1. Shoot length was 
significantly increased in aU concentrations of N salts studied. Sullivan and Daiber 
( 197 4) also reported increased shoot growth to ammonium nitrate treatment. Total 
leaf area was increased to 176% in N03 treatment at 30 mg r 1 and 277% in NH4 
treatment at 20 mg r 1 (Fig.2). Similar promoting effect was reported in B. gymnorhiza 
(Naidoo, 1990). High level of nitrate reductase activity was reported in several 
halophytes (Stewart eta!., 1972; 1973; 1979). However, in the present study in both 
treatments, NRA was found to be insensitive to added nitrogen owing to decreased 
nitrogen uptake because of competitive inhibition of ammonium ions by sodium 
(Naidoo, 1987), chlorides, deficiency of 02 in the rhizosphere and by metabolic 
Moorthy and Kathiresan: Nitrogen form and growth of a mangrove 135 
30 
Rl-NH4 8. RL-NOJ CJ SL-NH4 
25 
-
SL-NOJ 4 LA-N9J 
20 
15 
10 
5 
0 
0 5 10 20 30 40 50 100 
Concentration (ma I-' 
150 200 250 
Fig.l. Root length (RL;cm) Shoot length (SL;cm) and Leaf area (LA;cm2) as 
1 
influenced by nitrogen treatments in seedlings of R. apiculata. 
-Q 
0 
~ 
..J 
0 
w 
w 
0 
..... 
« 
w 
II-
!:( 
:E 
>-
« 
0 
2 
ROOT- NH4 
-
ROOT- N03 
EJ SHOOT- NH4 
1.5 
-
SHOOT- No
3 
1 
0.5 
oc.-. .......... __.""""' ........ __,.,_..,_,."""'"'~ 
0 5 10 20 30 40 50 .100 150 200 250 
Concentration (mg 1-~ 
Fig. 2. Dry matter accumulation in shoot and root growth of R. apiculata seedlings as 
influenced by nitrogen treatments. 
136 Pakistan Journal of Marine Sciences, VoL4(2), 1995. 
poisons such as hydrogen sulphide (Mooris, 1980). Total tissue nitrate content also 
followed a similar pattern. 
The content of photosynthetic pigments increased in seedlings treated with both 
forms of N. Nitrate treatment increased the chlorophyUs (a+b) content to 49%, 
reaction centre and light harvesting complex (LHC) chlorophyll to 96 and 29% at 50 
mg r 1. Likewise, NH4 treatment also promoted the chlorophyll (a+b), reaction centre 
and LHC chlorophyll to 74,99 and 63% respectively at 100 mg r 1 (Table I). 
Table I. Leaf pigments of R. apiculata seedlings as influenced by ammonium 
and nitrate form of nitrogen. 
Concentration 
of chemical 
(mg r 1) 
Control 
5 
10 
20 
30 
40 
50 
100 
150 
200 
250 
LSD5% 
Chlorophyll (a+b) 
(mg g-1 FW) 
NH4-N N03-N 
0.892 1.021 
1.363* 1.360* 
1.330* 1.553* 
1.089* 1.285* 
1.631 * 1.325 * 
1.270* 1.103 
1.334* 1.521 * 
1.553* 1.244 * 
1.314 * 1.152 * 
1.570* 1.426* 
1.429* * 1.211 
0.110 0.090 
*Significant at 5% level 
Reaction centre 
chlorophyll 
(mg g-1 FW) 
NH4-N N03-N 
. 0.275 0.300 
0.552* 0.549* 
* 0.526* 0.533 
oAoo* 0.402* 
0.612* 0.440 * 
0.507* 0.340* 
0.514* 0.587* 
* 0.450* 0.537 
0.485* 0.390* 
0.638* 0.601* 
0.602* 0.399* 
0.050 0.033 
SD values are less than 10% of mean values. 
LHC chlorophyll ·Carotenoids 
(mg g-1 FW) 
NH4-N N03-N 
0.316 0.316 
0.407* 0.400 
0.399* 0.514* 
0.345* 0.442 * 
0.509* 0.443 * 
0.382* 0.381 
0.410* 0.467* 
o.5o8* 0.397 
0.415* 0.381 
0.466* 0.413* 
0.414* 0.403 
0.030 0.051 
(j.! mol g -l FW) 
NH4-N N03-N 
0.182 0.205 
0.266* 0.280* 
0.256* 0.318* 
0.194 0.260* 
0.292* 0.256* 
0.228* 0.227 
0.253* 0.286* 
0.301 * 0.228 
0.252* 0.225 
0.286* 0.252* 
0.250* 0.241* 
0.025 0.035 
Content of carotenoids were also enhanced by 40 and 66% in N03 and NH4 
treatments at 50 and 100 mg r 1. Thus an increase in chlorophyll content in protein 
complexes represents a well organised LHC (also it is evident by higher amount of 
carotenoids), hence, promotion in primary reactions of chloroplast in the treated 
seedlings might have taken place. Of the two forms of nitrogen studied, NH4-N was 
found to be better in accumulating photosynthetic pigments than N03-N. Ammonium 
treatment enhanced the dry matter accumulation, shoot length, nitrate utilisation 
efficiency, content of photosynthetic pigments than the prop a gules treated with 
N03-N. Similar response of many halophytes to added nitrogen especially to NH4-N 
is weU documented in Avicennia marina (Naidoo, 1987) and a sea grass meadow 
(Tyler, 1967). This is in accordance with the natural habitat of mangrove which 
contains ammonium as a primary source of dissolved inorganic nitrogen due to the 
reduced conditions of soil as a result of water logging and anaerobic sediments 
Moorthy an.d Kathiresan.: Nitrogen. form an.d growth of a man.grove 137 
(Naidoo, 1987). It is concluded from the study that the propagules of R. apiculata 
can. be treated with NH4Cl prior to plan.tin.g in. n.ursery or in. n.atural condition. for better 
establishment an.d rootin.g an.d hen.ce suggested for artificial regeneration. of the 
mangroves. 
ACKNOWLEDGEMENTS 
The authors are than.kful to the Tamil Nadu State Coun.cil for Scien.ce an.d 
Technology, Madras for fin.an.cial assistance an.d to Prof. V. Ramaiyan., Director of 
this Cen.tre, Prof. T. Govin.darajulu, Dean., Faculty of Scien.ce an.d authorities of 
An.n.amalai University for providing facilities. 
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(Received: l June 1994) 


Influence of nitrogen salts on growth and physiological responses of Rhizophora apiculata Blume in non-aerated water culture

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Influence of nitrogen salts on growth and physiological responses of Rhizophora apiculata Blume in non-aerated water culture

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