Altered Leaf Photosynthetic Rate, Root Oxidizing Power and Yield of Rice Under Drip Irrigation.

Altered leaf photosynthetic rate, Root Oxidizing Power and yield of rice under drip irrigation T. Parthasarathi1*, K. Vanitha2, S. Mohandass3 and Eli Vered4 1 & 3. Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India; 2. Tamil Nadu Rice Research Institute, Tamil Nadu Agricultural University, Aduthurai 612101, Tamil Nadu, India; 4. Netafim Irrigation, Derech Hashalom, Tel Aviv, Israel 67892. *Email: tparthasarathicrp@gmail.com Abstract Rice grown in oxygenated condition had higher root activity and larger root absorption area, which favors crop growth. So, the root activity of rice was tested under drip irrigation during Dry Season (DS), 2011 and Summer Season (SS) 2012 in Coimbatore, Tamil Nadu, India. Drip irrigation treatments comprised of three levels of lateral distance (0.6, 0.8 or 1.0 m lateral distance), two micro irrigation methods such as surface, sub surface drip irrigation (SDI) with two discharge rates (0.6 or 1.0 L h-1 emitters). Root characters such as production of newer roots, root colour (White roots) root density, Root Oxidizing Power and Root Activity were showed better under drip irrigation methods due to root zone irrigation and fertigation. Increasing trend of root activity was observed at flowering stage and declined slightly at grain filling stage. Root activity of fresh root, photosynthetic rate of leaf remarkably accelerated in 0.8 m LD under Subsurface Drip Irrigation using 1.0 L h-1 drippers. Interactively, laterals spaced at 0.8 m with 1.0 L h-1 drippers laid sub surface-drip through fertigation exhibited better performance in terms of root parameters (such as root length, Root density, root oxidizing power and root activity) along with growth attributes (Leaf Area Index, Crop Growth Rate and Net Assimilation Rate), photosynthetic rate, yield and its components (such as productive tillers, spikelet numbers, filled grain percentage and Harvest Index) along with water productivity when compared with the conventional irrigation treatment. Root activity has immediate, strong and direct effects on leaf photosynthesis (0.936**) under drip irrigation practice. Therefore, it is suggested that the lateral spacing of 0.8 m with 1.0 L h-1 drippers when the plants spaced at 20 ? 10 cm with SDI through fertigation is adjudged as the best treatment for aerobic rice cultivation in enhancing the values for photosynthetic rate, water productivity and grain yield. Keywords: drip irrigation, grain yield, photosynthetic rate, root activity