drought

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1. What the characteristics of an ideal drought tolerant crop plant could be?

Drought is considered as the most important environmental constraint affecting the plant growth and agricultural productivity worldwide. Climate change models predict drought to become worse. Drought stress could occur when the availability of water for plant is limited and the plant water demands exceed water supply. Many factors could lead to drought conditions, soil dryness, high evaporation, osmotic binding in saline soils, and inadequate water uptake by plant in the shallow soils. Under drought stress, susceptible plants would not be able to survive. The plants that will survive under this condition either escape (avoidance) or compete (tolerance) with drought stress. To improve drought tolerance in crops, the ideal plant must be able of acclimating drought stress by increasing survival rate, and at the same time maintaining high yield, by stabilizing the same level of photosynthesis under stress condition. Specifically by:
- Early sensing of the water deficit, which would help the plant to quickly respond to the upcoming stress and be ready to oppose to the drought stress.
- Quick response of water uptake by root, once faced drought condition by having more extensive root system (deeper roots and more lateral roots) (Yu et al., 2008).
- Reduce water loss such as low leaf stomatal density (Yu et al., 2008) and stomatal closure. Seeing that high water loss through leaf transpiration occurs at stomata, better control of transpirational water loss via the stomata could be key component of drought tolerance plant.

2. The molecular characteristics that ideal drought tolerance plant should have

Drought tolerance is a quantitative trait, many genes...

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...ly alert the plant by activating the drought-tolerance related gene NCED3. The expression of NCED3 will cause the increase in endogenous ABA level in root and leaves.

I) Accumulation of ABA and it effect on the root growth
ABA then activate transcriptional factor (TF), particularly in ABA dependent path, such as CBF4 (C-repeat binding factor4) or HDG11. Consequently, these TFs will active their target genes downstream e.g. LEA3 or P5CS gene. The activated LEA and P5CS will cause root grow deeper and more lateral roots, leading to drought tolerance in plant. (Figure 1)

II) Accumulation of ABA and its effect on stomatal closure
Accumulation of ABA in the leaf apoplast, leading to increased ABA at the guard cells to initiate closure and inhibits opening (Wilkinson and Davies 2002) through a physiological series of steps in response to water deficit (Figure1).

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