Bulbs Geophytes: Nature's Bio-computers We live in an age of complex microcomputer technology that allows us to store and process huge amounts of knowledge and information in tiny amounts of space. But we haven't yet reached the level of a bulb to store life in a neat little package, safe from cold and drought. Locked in its protective and nourishing fleshy scales, a true bulb is a tiny life form- complete with roots, stems, leaves and flowers that waits through long, cold weather to burst forth into the sunlight of spring. This little nature-designed bulb package can continue to come alive year after year, completing the cycle of growth and dormancy many times over. The unique structure allows them to store food to carry them over during cold or dry weather conditions until their aboveground growth begins again. What is being stored? After a flowering bulb finishes blooming for the year, the energy produced through photosynthesis in the remaining leaves is stored for the next season in the bulb. For simplicity, we generally consider any plant that stores the energy needed for the next season's growth in an underground fleshy organ a bulb. But, actually only some of these plants are true bulbs! Bulbs are Geophytes; They're Special Any plant with an enlarged underground storage organ can be called a 'flowering bulb.' But horticulturists and botanists do distinguish between the different storage types depending on their anatomy: bulbs corms rhizomes tubers tuberous roots hypocotyls -all of these underground storage types are geophytes, or plants with enlarged underground storage organs. All storage organs serve the same purpose - storage of reserve substances that allow rapid growth when environmental conditions are favorable. Tulip, a true bulb A bulb, strictly speaking, has enlarged scales where most of those nutrients are stored and a small basal plate, which is where the next season's roots and shoots are. A corm is just the opposite: it has small scales and the nutrients are stored in the enlarged basal plate. Rhizomes and tubers are two different types of enlarged stems, which store the nutrients. Tuberous roots are (no surprise) enlarged roots serving as storage organs. A hypocotyl is the part of the newly germinated seed that lies between the cotyledons (seedling leaves) and the root. This enlarged area is like an oversized seed, where the nutrients are stored. Bulb Quiz Did you know that geophytes have been a part of people's diet since the begining of civilization? The bulbus portion of plants have been the plant's storage system for food energy when they are dormant, but they can also provide people with food energy when we eat them. These foods are all geophytes - can you match them with the kind of storage type they are? (Bulb - Corm - Rhizome - Tuber - Tuberous root - Hypocotyl) onions sweet potatoes carrots kohlerabi Jerusalem artichokes garlic potatoes beets alfalfa sprouts Teacher Tip Provide groups of students with samples of each of these geophytes- a grocery store trip should provide the samples. Allow students to explore each storage organ, examining and dissecting it, then noting differences and similarities in journals before taking the Bulb Quiz. Print and use this chart for your Bulb Quiz: Bulb Quiz Chart Discuss your conclusions, supporting your answers with a research trip to the media center. How many did you correctly label? Take Care of Me--I'm Alive Student gardeners in Minneapolis The storage organ under the ground is never physiologically dormant even when aerial growth is halted. Even though we call this 'dormancy' It continues to change and constantly senses its environment - like a biocomputer. That's why you must let the leaves stay on tulips, daffodils, lilies and other flowering bulbs after they're done blooming; if you cut off the leaves, the bulbs have no way to collect sunlight and convert it into food for next year's blooms. Bulbs native to temperate regions have adapted to the prolonged cold of winter by requiring a certain period of chilling before they'll break dormancy. This helps prevent the plants from, in essence, being fooled into thinking it's spring during an early warm spell, such as a January thaw. If the plants were to grow then, the tender growth would be killed by the next hard freeze. The chilling requirement is an adaptation to ensure that the plants won't sprout until spring has really arrived. Copyright 2002- 2004 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to jn-help@learner.org