Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 1995
Publication Date: N/A
Interpretive Summary: The lack of sufficient levels of iron, an essential metal nutrient in living organisms adversely affects proper growth and development. Deficiencies in iron are common in certain key agricultural areas and decrease crop production. Iron is supplied to the plant through the roots by active, well-regulated processes. Furthermore, deficiencies in iron trigger root responses that enable the roots of certain plants to take up more iron from the soil. A better understanding of these processes is needed to devise methods to provide crops with sufficient levels of iron in an economical and sustained manner. A problem associated with understanding these processes is the interference caused by competing soil microorganisms. To address this problem, the research described in this paper deals with the development and use of a method to grow plants under sterile conditions and under iron stress. The results of this paper show that the responses of roots to iron-deficiency of plants grown in the sterile hydroponic culture system are the same as those grown under non-sterile conditions. This sterile system will greatly facilitate future studies of root activities, free of microbial interference, under a variety of environmental and nutirent stresses.
Technical Abstract: A sterile hydroponic culture system (SHCS) suitable for studying iron chlorosis in vitro was developed. This system, consisting of a 38 x 200 mm culture tube, a Kap-ut closure, a foam platform, and an aluminum sleeve, resembled a greenhouse hydroponic system. In this SHCS the plants were positioned upright within the culture tube using the foam plug platform; the roots are submerged in liquid Murashige and Skoog basal medium (basal medium) containing 3 percent sucrose. Onion plants (Allium sativum L. cv.'Sweet Spanish, Yellow Utah Jumbo'), grown in the SHCS on basal medium without FeEDTA exhibited gradual chlorosis, i.e. leaf yellowing, with leaf SPAD values of 34.9 plus/minus 1.9 at the end of 8 wks. Non-chlorotic plants grown in the SHCS on basal medium with 80 uM FeEDTA had leaf SPAD values of 51.3 plus/minus 2.3. Gradual regreening of leaves was achieved when chlorotic plants were recultured into basal medium with FeEDTA. The occurrence of Fe-deficiency responses in the roots of the chorotic plants grown in the SHCS was tested. The stimulation of root surface electron transfer, a typical Strategy I response to Fe-deficiency, is further shown by the rapid FeHEDTA reduction by the roots of the chlorotic, sterile-grown onion plants. roots is presented. The stimulation of root surface electron transfer, a typical Strategy I response to Fe-deficiency, is further shown by the rapid FeHEDTA reduction by the roots of the chlorotic, sterile-grown onion plants.