MadSci Network: Botany
Query:

Re: Where do plants store their food?

Date: Mon Feb 16 18:17:00 2004
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1076968863.Bt
Message:

Many plants temporarily store starch in their chloroplasts. Students often 
test leaves for starch. Starch is a polymer of glucose. 

About 15% of flowering plant species do not store carbohydrates as starch. 
Wheat, barley, onion, Jersusalem artichoke and other species make fructans 
instead of starch. Fructans are polymers of fructose and are stored in the 
cell vacuole. In plants that store mainly sucrose, such as sugar cane, the 
sucrose is also found in the vacuole. 

Seeds store starch or other carbohydrates, proteins and/or oils. These 
nutrients are intended to nourish the developing seedling. Starch is stored in 
plastids termed amyloplasts. Oil storage plastids are termed elaioplasts. 
Protein storage plastids are termed proteinoplasts or proteoplasts. For some 
photos of plastids, search Visuals 
Unlimited.

In angiosperms, the seed nutrients may be stored in the triploid (3n) 
endosperm, as in corn, wheat and rice; in the cotyledons of the embryo, as in 
bean and peanut, or in both endosperm and cotylelons. In gymnosperm seeds, 
such as, pine and spruce, the nutrients are in the cotyledons and the haploid 
(1n) female gametophyte. 

Seeds are the most important source of human food because of their 
carbohydrate, protein and oil content. Corn, wheat and rice are the world's 
most important crops. Corn is found in thousands of processed foods often as 
high fructose corn syrup or corn starch. Almost all cooking oils are obtained 
from seeds. Examples of cooking oils include soybean oil, corn oil, canola 
oil, cottonseed oil, coconut oil, peanut oil, safflower oil, sunflower oil and 
sesame seed oil. 

Many plants have specialized underground storage stems such as corms (crocus, 
gladiolus), tubers (potato) and rhizomes (ginger and iris). Sugarcane stores 
large amounts of sucrose in its aboveground stems. 

Many plants have roots specialized for storage, such as carrot, beet and sweet 
potato. Sugar beets store large amounts of sucrose in their storage roots.

Bulbs store nutrients in fleshy leaves. Familiar bulbs are onion, garlic, 
lily, tulip, daffodil, hyacinth and amaryllis.

Fruits are not really areas of nutrient storage for the plant because the 
plant or its offspring cannot use the stored nutrients. Nutrients stored in 
fruits are designed to attract animals to eat the fruit and thereby disperse 
the seeds.

References


Testing a leaf for Starch


Basic Fructan Info


Modified Roots, Stems and Leaves


A Zillion Uses for Corn



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