Drought Stress

Name the four mechanisms by which plants can tolerate drought. Define one of these mechanisms in detail and provide an example

(1) Drought escape (rapid development and maturity before water runs out),

(2) dehydration avoidance (avoiding tissue water loss by stomatal closure, deep rooting, and other means),

(3) optimum resource partitioning (such as increasing the root to shoot ratio or maintaining growth of plant parts like flowers and young seeds which are vulnerable to abortion or arrested development), and

(4) desiccation tolerance (plant tissues dry but do not die due to specialized proteins and solutes as in dry seeds).

What cellular processes in the plant are most sensitive to drought?

The most sensitive processes are those dependent on turgor pressure such as expansion growth, and responses that respond to sensing of turgor loss, such as stomatal closure.

At what stage of growth is corn yield particularly vulnerable to water deficit?

At silking (flowering) and early kernel formation. At these early stages of reproductive development the maize regulatory system is poised to abort reproductive capacity if resource acquisition (whole plant photosynthesis, nitrogen, etc.) is gauged insufficient to provide sufficient future nourishment through grain starch filling and maturity. Prior to recent breeding efforts, maize tended to be quite conservative such that too much floret and kernel abortion took place and yield suffered greatly.

Name at least two types of irrigation systems.

(1) surface flooding,

(2) sprinkler or center pivot sprinkler, and

(3) drip (surface or sub-surface) via plastic tubing.

Why would a farmer monitor canopy temperature?

Canopy temperature indicates the extent of evaporative cooling due to transpiration. When water becomes so limiting that stomata close, leaves heat up relative to surrounding air temperature. Farmers can use this information in irrigation scheduling.

What is the global aridity index?

how dry different regions are on average.

What are the four main types of droughts?

1. Meteorological drought - when an area experiences a prolonged period of unusually dry weather.

2. Hydrological drought - reduced water levels in rivers, reservoirs, and groundwater (Often caused by longterm meteorological drought)

3. Agricultural drought - Not enough soil moisture to support crops or livestock

4. Socioeconomic drought - Demand for economic goods > Supply