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Effects of Local Variations in Soil Moisture on Hydrophobic Deposits and Dye Diffusion in Corn Roots
Author(s) -
Watt M.,
Weele C. M.,
McCully M. E.,
Canny M. J.
Publication year - 1996
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1996.tb00602.x
Subject(s) - soil water , water content , thermal diffusivity , diffusion , chemistry , endodermis , soil horizon , botany , soil science , biology , geology , physics , geotechnical engineering , quantum mechanics , thermodynamics
The effects of local soil water content (SWC) alone on the development of hydrophobic deposits and on diffusivity of root tissues were studied in primary roots of maize seedlings whose top regions were growing at a constant rate in damp soil. Corn primary roots were grown through 30 cm‐profiles of soil with pre‐set dry (8% SWC), or wet (23% SWC), middle layers, and moist (15% SWC) top and bottom layers. When the root tissues in the soil of variable SWC were maturing (approximately 17% of the total root length), the tips of the roots were in damp soil several centimeters away and growing at the rate characteristic of this environment. Histochemistry and fluorescence microscopy on root sections of similar age showed that in these roots local SWC had no effect on hypodermal and endodermal suberization: both had equally developed Casparian bands and suberized lamellae. However, local SWC did alter the hydrophobic deposits in the walls of the epidermis; they increase in dry soil. To study tissue diffusivity, root portions from dry or wet soil were divided in the transverse direction, and half was dipped in sulphorhodamine G (SRG), sectioned, and observed with fluorescence optics. The other half was studied with a cryo‐scanning electron microscope to observe the contents of the cortical intercellular spaces. The rate of SRG diffusion in a portion of root from dry or wet soil was independent of local SWC but was positively correlated with numbers of fluid‐filled intercellular spaces. The implications of these observations for the movements of ions through the root cortex are discussed.