Water stress: scarcity as ripening control

The standard

A controlled water balance measures how far supply falls short of need, and judges the stress by that gap, not by the mere absence of rain.

Criteria

• The deficit is measurable, through leaf water potential or soil moisture
• It occurs in the ripening-relevant phase, not at random
• It stays below the threshold at which photosynthesis ceases
• Its effect shows in growth and fruit ripening, not only in the soil

Distinction

Water stress ≠ drought: drought describes the climate, water stress the condition of the plant within it. Water stress ≠ drought damage: up to a limit the controlled water balance steers ripening, beyond it the deprivation harms the vine.