Crop Growth and Development Flashcards

Which of the following correctly describes the source-sink relationship during grain fill?

Answer: Leaves and stems are sources supplying photosynthate to grain sinks

During grain fill, leaves and stored stem carbohydrates act as sources, translocating photosynthate to the developing grain (sink).

The concept of 'critical period for weed control' in a crop refers to:

Answer: The period during which weed competition most significantly reduces crop yield

The critical period for weed control is the crop growth window during which weeds must be removed to prevent economically significant yield loss.

Stomatal conductance primarily regulates which two processes in plants?

Answer: Gas exchange (CO2/O2) and transpiration

Stomata control CO2 uptake for photosynthesis and water vapor loss through transpiration, balancing carbon gain against water loss.

Crop lodging refers to:

Answer: The permanent displacement of plant stems from vertical to a prostrate position

Lodging occurs when plant stems or roots fail, causing plants to fall over, which reduces yield, harvest efficiency, and grain quality.

Which type of seed dormancy is broken by exposure to light and is common in small-seeded species?

Answer: Photodormancy (light-mediated dormancy)

Photodormancy is regulated by phytochrome and requires specific light exposure to break dormancy, common in lettuce and some weed species.

In wheat, the Zadoks scale stage Z65 (anthesis) is critical for yield because:

Answer: Fertilization of florets determines the number of kernels per spike

At anthesis, pollen release and fertilization determine the number of kernels set per spike, a primary yield component in wheat.

Harvest index (HI) is defined as the ratio of:

Answer: Grain yield to total above-ground biomass

Harvest index is the proportion of total above-ground biomass that is grain, reflecting how efficiently a crop partitions photosynthate into harvestable yield.