Answer to Question from Last Issue (6-3-2020) – Vegetable Crops Hotline

Answer to Question from Last Issue (6-3-2020)

Question: Why are the water droplets arranged so evenly around the edge of this cucurbit leaf?


The water droplets came out of pores that are at the edge of the leaf where a vein ends. The pores are called hydathodes. The droplets form through the process of guttation. Guttation is when the water pressure in the plant is high enough to force water out of the hydathodes. This occurs when soil moisture and humidity are high, typically at night during rainy humid weather.

The hydathodes may also serve as a means for bacterial pathogens to enter leaves. The water droplets can be drawn back into the plant as the sun comes out, relative humidity drops, and the leaf begins to lose water through transpiration. When bacterial diseases are present, these water droplets can be a major means of disease spread if people,  animals,  equipment, wind, or rain move water droplets containing bacteria from one plant to another.

For instance, see how the angular leaf spot on this cantaloupe leaf starts at the leaf margin and moves down the vein.

Black rot of cabbage and other crucifers also can enter through hydathodes and spread down the veins.

Share This Article
It is the policy of the Purdue University that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue is an Affirmative Action Institution. This material may be available in alternative formats. 1-888-EXT-INFO Disclaimer: Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer.
Vegetable Crops Hotline - Horticulture & Landscape Architecture, 625 Agriculture Mall, West Lafayette, IN 47907

© 2021 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Vegetable Crops Hotline

If you have trouble accessing this page because of a disability, please contact Vegetable Crops Hotline at