Germination
Studies conducted in Australia indicated that waterlogging
decreased germination if soil was saturated for more than
3 days (Mc Mahon et al. 1993). Flooding during planting
affects emergence. Sugarcane variety CP 89-2376 showed
more shoot emergence with less than 6 days of flooding
whereas CP 72-2086 showed extremely low emergence.
Varieties with more shoot emergences would reduce losses
due to flood at planting caused by heavy rains.
Root System Under Waterlogging
The immediate effect of water logging is observed in the
soil i.e., conversion of aerobic environment to anaerobic
environment due to deficient aeration, thereby affecting the
growth and functioning of roots. In the absence of oxygen,
root hairs die and eventually the roots blacken and rot with
the result entire under ground root system gets choked and
root respiration is also impaired. Because of the insufficient
and inadequate root system absorption of nutrients and
water is seriously affected. Nutrient absorption is further
affected by their unavailability leading to nutrient deficiency
symptoms. Due to improper root system absorption
of water is hampered resulting in ‘‘Physiological Drought’’.
The plant leaves assume a tightly curved position similar to
the condition observed during moisture stress.
Root Survival in Anaerobic Conditions
Waterlogging can cause hypoxia, a situation causing deficiency
of oxygen in the soil environment and anoxia, a
condition that refers to complete absence of oxygen in a
defined soil environment, leading to arrest of root respiration
completely and affecting important metabolic
activity of the plants. Under such situation roots survive
either by inducing biochemical or anatomical acclimation.
Following sensing of partial oxygen deficiency, genes
coding for anaerobic proteins (ANPs protein) are up-regulated
at transcriptional and post-transcriptional levels and
the ANPs are necessary for the acclimation (Jackson 2003).
Anaerobic proteins can be divided into,
1. Enzymes involved in starch breakdown,
2. Enzymes implicated in pH regulation,
3. Enzymes involved in aerenchyma formation
4. Enzymes with protective function (free radical scavenging
enzymes)
5. Proteins involved in signal sensing and transduction
(ethylene receptor)
6. Others of unidentified function.
Anatomical Adaptation Through Aerenchyma
Formation
In waterlogged condition, sugarcane is supported by
adventitious roots which develop possibly as a result