Previous PageTable Of ContentsNext Page

Dry matter and nitrogen remobilization of rice genotypes under different transplanting dates

Z.Tahmasebi Sarvestani, and H.Pirdashty

Department of Agronomy, College of Agriculture, University of Tarbiat Modarres, Tehran, Iran.

ABSTRACT

To investigate the effects of transplanting dates and rice genotypes on remobilisation of dry matter and nitrogen and yield components, a field experiment was carried out in the Rice Research Institute (Amol, Iran) in 1998. The treatments were arranged in a factorial design with 3 replications. Dry matter and nitrogen remobilisation of shoot (stem + leaf + flag leaf) had an important effect on grain dry matter and nitrogen accumulation. However the amount of dry matter and nitrogen remobilisation was different under different transplanting dates and different genotypes. There were a significant effect and positive correlation between yield and nitrogen remobilisation. The remobilisation of dry matter and nitrogen from different parts of the shoot to the grain responded differently. Differential responses to the treatment and also in different parts of the shoot suggest that the remobilisation of dry matter and nitrogen be controlled through different mechanisms.

Key words

Rice, yield, dry matter, nitrogen, remobilisation, transplanting date.

INTRODUCTION

Two physiological process are involved in grain growth: utilization of photosynthates through current photosynthesis, and remobilisation and translocation of substance accumulated before anthesis (Akita, 1989). Cock and Yoshida (1971) and Marsehner (1993) reported that about 20 % to 40 % of the grain carbohydrate are from previously stored carbohydrate. On the other hand, stem carbohydrate reserves have been estimated to contribute about 18% of the final grain yield in rice under normal condition (Venkateswarlu, 1976). During ripening, however, nitrogen accumulates in the spikelet of the ear mainly as protein and the protein content at harvest accounts for 8-10 % of the final dry matter content (Iwasaki et al, 1991). Tahmasebi Sarvestani et al (1994) reported that in wheat plants among different parts of the shoot the remobilisation of dry matter was greater from the internode than other parts of the shoot and there were comparatively small amount of these compounds remobilized from the leaves. On the other hand, leaves were the most important parts of the shoot in terms of the remobilisation of nitrogen. During the grain filling period, N is gradually translocated from the vegetative plant parts to the developing rice panicles. We investigated the remobilisation of dry matter and nitrogen from the vegetative parts of different rice genotypes during grain filling under different transplanting dates.

MATERIALS AND METHODS

In 1998, a field experiment was conducted at the Rice Research Institute in Amol, Iran. Four rice varieties, Tarom (traditionally grown in Amol), Nemat, Fajr and Sahel (improved) were translocated on May 13,May 23 and June 1. The treatments were arranged in factorial design with 3 replications. Seedlings of the four varieties were grown for 40 days in semi-irrigated nursery beds. Three seedlings per hill were transplanted by hand at a density of 25 * 25 cm. Nitrogen, phosphorus and potassium were applied at the rate of 150-100-100 kg ha-1 respectively which is enough for potential production in Amol conditions. Half of the N and full doses of P and K were applied at transplanting and the remaining N was applied at tillering and panicle-initiation stages in 2 equal splits. Water management, weeds, pests and diseases were controlled to satisfy the requirement for potential production. At the flowering and the maturity, plants were collected and separated different parts were dried under 75 ˚C during 72 hours and then weighed. The total nitrogen content of each sample was determined by the Kjeldahl- digestion method. Amount of dry matter and nitrogen remobilisation accounted as followed:

Amount of dry matter or nitrogen remobilisation (mg per plant)= amount of dry matter or nitrogen at flowering minus amount of dry matter or nitrogen at maturity except grain. The data were analysed by analysis of variance.

RESULTS AND DISCUSSION

Dry matters were lost from different parts of the shoot of different varieties under different transplanting dates between flowering and maturity (Table 1). Stem of all varieties remobilized about 6-10% of dry matter between two harvests (Table 1). More dry matter was remobilized from the stem and flag leaf of Fajr variety. Among different transplanting date, second transplanting date (May 23) was the best transplanting date in term of dry matter remobilisation in Amol environmental conditions. On the other hand, leaves (flag leaf + other leaves) of all rice varieties remobilized more nitrogen than stem under all conditions (Table 2). Dry matter and nitrogen remobilisation had important effect on grain dry matter and nitrogen accumulation. In sahel variety dry matter in first transplanting date (May 13) and third transplanting date (June 1) contributed approximately to 50.13%(highest) and 16.32%(lowest) of grain dry matter respectively. Among different parts of the shoot leaves (flag leaf + leaves) had more important effect on grain nitrogen accumulation.

Table 1. Dry matter changes from different parts of the shoot during flowering to maturity (mg per plant)*

Source of Variation

Remobilisation

Accumulation

Stem

Other leaves

Flag leaf

Total

Grain

Transplanting Date
13 May 1998
23 May 1998
1 June 1998

Variety
Tarom
Nemat
Sahel
Fajr


379.17 b
450.00 a
277.50 c


298.89 c
355.56 b
387.78 b
433.33 a


63.33 a
63.33 a
66.66 a


84.44 a
71.11 b
68.89 b
33.33 c


22.50 a
16.67 b
20.83 ab


-7.78 d
1.11 c
38.89 b
47.78 a


465 b
530 a
364.9c


375.55d
427.78c
495.56b
514.44a


6051 a
5310 b
4516 c


4800b
5320a
4427d
4657c

Table 2. N changes from different parts of the shoot during flowering to maturity (mg per plant)*

Source of Variation

Remobilisation

Accumulation

Stem

Other leaves

Flag leaf

Total

Grain

Transplanting Date
13 May 1998
23 May 1998
1 June 1998

Variety
Tarom
Nemat
Sahel
Fajr


5.44 a
4.51 b
2.43 c


4.97 a
4.24 b
4.07 b
3.24 c


4.10 b
5.31 a
5.28 a


4.31 c
5.62 a
4.40 c
5.27 b


4.10 b
5.31 a
5.28 a


4.31 c
5.62 a
4.40 c
5.27 b


11.61b
12.81a
10.6c


10.63c
13.08a
10.54c
12.47b


116.46
99.9
121.59


105.67a
78.97b
65.15c
60.32d

*Means followed by the same letters in each column are not significantly different according to Duncan’s Multiple Ranges Test.

CONCLUSION

Result of the present study indicate that there is a difference in dry matter and nitrogen remobilisation in different varieties and transplanting dates under Amol weather conditions. Differential responses to the treatment and also in different parts of the shoot suggest that the remobilisation of dry matter and nitrogen be controlled through different mechanisms. This result can help physiologists and breeders to determine physiological and morphological features of varieties that contribute most to increasing yield production.

REFERENCES

1. Akita, S. 1989. Genotypic Variation in Mineral Uptake of Rice Mutant and Parent.3th Ed. (Los Banos, Philippines).

2. Cock, J. H. and Yoshida, S.1971.Proceeding Crop Science Society of Japaneses. Vol. 41, 226-234.

3. Iwasaki, Y., Mae, T., Makino, A., Koji, O. and Ojima, K. 1992. Soil. Sci. Plant Nutrition. 38, 517-525.

4. Marsehner, H. 1993. Mineral Nutrition of Higher Plants. 2nd Ed. (Stuttgart, Germany).

5. Tahmasebi sarvestani, Z, Jenner, C.F. and McDonald. 1994. Proceedings 44th Australian Cereal Chemistry Conference. Ballarat, p247-50.

6. Venkateswarlu, B. 1976. Plant and soil .44, 575-586.

Previous PageTop Of PageNext Page