1. Root Morphology and Anatomy of Rice Plants Cultivated under System of Rice Intensification (SRI)
Nurul Hidayati1, Triadiati2*, Iswandi Anas3
1Plant Biology Study Program, Graduate School, Bogor Agricultural University (IPB), Bogor, Indonesia
2 Department of Biology, Faculty Mathematics and Natural Sciences, Bogor Agricultural University (IPB), Bogor, Indonesia
3 Soil Biotechnology Division, Faculty of Agriculture, Bogor Agricultural University (IPB), Bogor, Indonesia
*Corresponding author: adiatiipb@gmail.com
ABSTRACT
Significant increases in rice yield cultivated under the System of Rice Intensification (SRI) under different ecological/climatic conditions have been reported by many researchers. Development of rice roots surely plays a very important role in the uptake of water and nutrients by rice plants. However, there are few studies on the impact of SRI cultivation methods on the morphology and anatomy of rice plant roots. This research evaluated such changes for rice plants cultivated under SRI methods com- pared to conventional rice cultivation methods. The research used randomized block design (RBD) consisting of two rice cultivation methods, namely SRI and conventional rice cultivation practices. With SRI cultivation methods, transplanting was done at the seedling age of 10 days, one seedling per hill with planting distance of 25 cm x 25 cm, with saturated irrigation method but no flooding In conventional rice cultivation methodology, transplanting was done at the seedling age of 25 days, three seedlings per hill, with hill-to-hill distance of 20 cm x 20 cm , with continuously flooded soil. The fertilization for both sets of treatments was the same, i.e., 125 kg Urea/ha, 100 kg SP-36/ha, 50 kg KCl/ha, and 2.5 tons of organic matter/ha. Under SRI cultivation, roots were significantly longer and their biomass was significantly heavier than for conventional management. More root hairs and healthier root hairs were observed on rice plants under SRI cultivation compared to conventional practice. Also, the numbers of aerenchyma (air pockets) in plant roots were seen to be less under SRI cultivation compared to conventionally-grown rice plants, while at the same time, the numbers of aerenchyma in plant stems were the same with both cultivation methods. However, the size of stem aerenchyma under SRI was significantly smaller than under conventional rice cultivation. No significant difference was found in root respiration between rice plants cultivated under the two methods.
Key words: System of Rice Intensification (SRI), conventional rice cultivation method, rice anatomy, aerenchyma
INTRODUCTION
Significant increases in rice yield cultivated under the System of Rice Intensification (SRI) under different ecological/ climatic conditions have been reported by many researchers. The application of SRI methods focuses in plant root development through different management of plants, soil, water and nutrients, while promoting more economic value. Managing plants, soil, water and nutrients so as to promote the growth and functioning of root systems is a core element of SRI (Uphoff 2005) so that plants can grow optimally.
The development and performance of rice roots surely plays a very important role in the uptake of water and nutrients by rice plants. There are few reports on the impact of SRI cultivation methods on the morphology and anatomy of rice plant roots, however. This research evaluated the changes in morphology and anatomy of rice roots cultivated under SRI methods compared to conventional methods of rice cultivation.
MATERIALS AND METHODS
This research was conducted in Sindang Barang Jero, West Java, and Laboratory of Plant Physiology, Department of Biology, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University, from October 2012 to September 2013. The materials used were Ciherang variety of seed, urea-based fertilizer (44.73% N), SP-36 fertilizer (38.94% P2O5), KCl fertilizer (59.90% K2O), and compost enriched with plant growth-promoting rhizobacteria (PGPR) (Bacillus sp., Pseudomonas sp., Azospirillum sp., and Azotobacter sp.), collection of the Laboratory of Microbiology, Department of Bi- ology, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University. Measurement of soil redox potential (Eh) used an Eh meter PRN-41 DKK TOA (Japan); measurement of root respiration followed the methods of Verstraete (Anas 1989) and Fu et al. (2008). The anatomical parameters were observed by scanning electron microscope (SEM), the Optilab stereo microscope, and the Optilab light microscope.
The research was designed according to randomized block design (RBD) in which the methods of rice cultivation used were 2 treatments: the conventional method (Kon) and the System of Rice Intensification (SRI) method. Each treatment was replicated five times. Experimental plots were each 4 m x 5 m (20 m-2).
RESULTS
ACKNOWLEDGEMENT
This study was funded by Lembaga Pengelola Dana Pendidikan (LPDP). We are grateful to staff of the Plant Physiology Laboratory, the Department of Biology, the Soil Biotechnology Laboratory, and the Department of Soil Sci- ence and Land Resources, Bogor Agricultural University (IPB) for their assistance.
CONCLUSIONS
SRI methods improved root length by 16.1% at 110 DAS and increased root dry weight by 64.5% at 70 DAS and by 67.3% at 110 DAS compared with plants grown conventionally. However, there was no difference in root respiration.
Aerenchyma formation in rice roots and stems with SRI method was seen to be lower than with conventional methods. The area of aerenchyma in rice roots was 45.1% under SRI management, while with conventional methods it was 71.0%, 26.5% less. The area of stem aerenchyma was decreased simultaneously by 42.3% in comparison to conventional practice. However, it was seen that the numbers of stem aerenchyma with SRI method and conventional method were no different.
The SRI method also increased the number of root hairs by 60.0% compared to conventional methods of rice cultiva- tion: older seedlings, closer spacing, continuous flooding of the soil.
a b
Effects of Cultivation Methods on Root Morphology
Figure 1 Root length (a) and root dry weight (b) at 70 and 110 days after sowing. Kon: Conventional; SRI: System of Rice Intensifica- tion.
Effects of Cultivation Methods on Root Respiration
Effects of Cultivation Methods on Anatomy Parameters
Table 1. Effect of cultivation methods on root and shoot aerenchyma (air pockets) at 70 days after sowing.
Conventional Conventional SRI
Conventional SRI
Conventional SRI
Figure 3. Observations of rice root aerenchyma at 70 days after sowing, using SEM JEOL JSM-5310LV type, magnification of 100x.
: aerenchyma.
Figure 4. Observations of rice stem aerenchyma at 70 days after sowing, using Optilab stereo micro- scope (Olympus type) and Optilab light micro- scope (Olympus CX21FS1 type), magnification of 20x (a), 40x (b), and 100x (c), respectively.
:Aerenchyma
Figure 5. Observations of rice root hairs at 70 days after sowing, using SEM JEOL JSM-5310LV type, magnification of 500x (a) and 1000x (b), respectively.
REFERENCES
Fu S, Zhou L, Shen J, Ding M, Zhang F, Huang H, Rao X, Lin Y, Shao Y, Zhang W. 2008. A simplified system for measur- ing rhizosphere respiration of fine roots in situ. Forest Ecology & Management 255: 3360–3364.
Uphoff N. 2005. Agroecologically-sound agricultural systems: Can they provide for the world’s growing populations? Keynote for 2005 Tropentag, University of Hohenheim. http://ciifad.cornell.edu/sri/articles/tropentagntu05.pdf
IRC14-0616
Conventional SRI
Conventional SRI
Conventional SRI
a
b
c
a
b
Figure 2. Root respiration at 4 phases of growth (V: vegetative; F: flowering; G: grain filling; M: ma- tures stage).
Conventional
SRI
Rice cultivation method
Number of root hairs per mm2
Conventional
510.41b
SRI
816.50a
Table 2 Effects of cultivation methods on root hairs at 70 day after sowing.
Rice cultivation method
Root aerenchyma
(%)
Number of stem aerenchy- ma per circumference
Stem aerenchyma area
(μm2)
Total stem aerenchy- ma area
(μm2/circumference)
Conventional
70.9b
27.8a
53,597b
1,491,835b
SRI
45.1a
27.0a
30,939a
83,5966a
a The same letters in the same column followed by the same letter are not significantly different.
a The same letters in the same column followed by the same letter are not significantly different.