Question

though water logging is harmful but why paddy crop is water logged (expain it)

Answer 1

paddy crop is strong influence by the water . so water should be keep standing in the feild throughout the period. because rice is semi aquatic plant
total water requirements for rice(paddy) is 1200-1400mm
2000 -3000 to grow 1kg of rice these all data shows that water is necessary for paddy crop

Answer 2

Answer:

Explanation:

Plants growing in flooded or waterlogged soil can die from lack of oxygen, as water fills the spaces between the soil grains and prevents respiration in root cells.

Rice is a crop that can flourish in flooded soils, whereas many other plants will die, so flooding of rice paddies is an important way to control weeds in rice fields. However, even rice plants can suffer yield loss or die if the water is too deep for a long time. In response to waterlogging, rice and many wetland plants form gas spaces called “aerenchyma” by inducing the death of cells inside the roots, allowing oxygen to be transported from leaves down to the roots. Aerenchyma thus play an important role in the survival of rice and other plants under waterlogged conditions.

In response to oxygen deficiency, root cells produce highly reactive molecules called reactive oxygen species (ROS). The concentration of calcium ions also increases prior to aerenchyma formation. These observations led Yamauchi et al. to think that ROS and calcium ions promote aerenchyma formation under waterlogged conditions. Their primary question was to understand how ROS and calcium ions might work together to promote aerenchyma formation in rice.

ROS and calcium ions are linked in reactions catalyzed by enzymes called Respiratory burst oxidase homologs (RBOHs) and calcium-dependent protein kinases (CDPKs). Calcium ions activate CDPK enzymes, which in turn activate RBOH enzymes, and activated RBOH produces a type of ROS called superoxide. Yamauchi et al. found that two rice CDPKs activate a rice RBOH, when expressed in leaves of the model plant Nicotiana benthamiana. The genes encoding these enzymes are highly expressed in rice roots under waterlogged conditions. Moreover, knockout of the RBOH in a rice mutant disrupted aerenchyma formation. These results showed that CDPK-mediated activation of RBOH is essential for aerenchyma formation in rice roots.

Curiously, only some cortical cells die while others do not during aerenchyma formation. The authors hypothesized that the cells that die have greater activities of these CDPK and/or RBOH enzymes. Future studies will focus on understanding how these enzymes are regulated in each root cell. Because flooding can cause tremendous crop yield losses, understanding how plants tolerate waterlogged conditions can help to develop improved rice varieties as well as other flood-tolerant crop plants.