MadSci Network: Botany

Re: Will a plant that needs water & sunlight live longer with water only or sun?

Date: Fri Mar 20 11:49:38 1998
Posted By: Eric Biddinger, Grad Student, Horticulture, Penn State University
Area of science: Botany
ID: 888339261.Bt

MadSci Network: Botany


This is something I have never really thought about.

Several things are required for a plant to live and grow:
Light, water, air, nutrients, good temperature, and physical support.
Obviously if you take away either water or sunlight, the plant will not survive for long.

But which will survive longer? Let's look at what water and sunlight do for the plant.

Plants make carbohydrates from sunlight by a process called photosynthesis. These carbohydrates can be stored in a plant until it needs the energy it has stored. A carrot, for example, store this extra food in its large root so it has food to grow the next year.

Water is used in the plant during photosynthesis and respiration (the process of turning the stored food into energy). So if there is no water, the plant can neither make food or use the food it has stored.

A couple of other factors will make a big difference for you run this experiment. What type of plant are you growing? A big cactus will have a lot more stored water than a tomato. How big/old are the plants. Seedlings that have just emerged from the soil use food stored in the seed until they are large enough to make all of their own food, so taking away light from these plants will not make a difference for several days.

Normally, I would say that a plant without sunlight will last longer than a plant without water.

Thanks for the question!

Eric J. Biddinger
Grad Student - Department of Horticulture
Penn State University

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