Root uptake under mismatched distributions of water and nutrients in the root zone

<p>Most plants derive their water and nutrient needs from soils where the resources are often scarce, patchy, and ephemeral. It is not uncommon for plant roots to encounter mismatched patches of water-rich and nutrient-rich regions in natural environments. Such an uneven distribution of resour...

Full description

Bibliographic Details
Main Authors: J. Yan, N. A. Bogie, T. A. Ghezzehei
Format: Article
Language:English
Published: Copernicus Publications 2020-12-01
Series:Biogeosciences
Online Access:https://bg.copernicus.org/articles/17/6377/2020/bg-17-6377-2020.pdf
_version_ 1819203691343773696
author J. Yan
N. A. Bogie
T. A. Ghezzehei
author_facet J. Yan
N. A. Bogie
T. A. Ghezzehei
author_sort J. Yan
collection DOAJ
description <p>Most plants derive their water and nutrient needs from soils where the resources are often scarce, patchy, and ephemeral. It is not uncommon for plant roots to encounter mismatched patches of water-rich and nutrient-rich regions in natural environments. Such an uneven distribution of resources necessitates plant reliance on strategies for exploring and acquiring nutrients from relatively dry patches. We conducted a laboratory study that elucidates the biophysical mechanisms that enable this adaptation. The roots of tomato (<i>Solanum lycopersicum</i>) seedlings were laterally split and grown in two adjacent, hydraulically disconnected pots, which permitted precise control of water and nutrient applications to each compartment. We observed that the physical separation of water-rich and nutrient-rich compartments (one received 90 % water and 0 % nutrients and the other received 10 % water and 100 % nutrients) does not significantly stunt plant growth and productivity compared to two control treatments (control 1: 90 % water and 100 % nutrients versus 10 % water and 0 % nutrients; control 2: 50 % water and 50 % nutrients in each compartment). Specifically, we showed that soil dryness does not reduce nutrient uptake, vegetative growth, flowering, and fruiting compared to control treatments. We identified localized root proliferation in nutrient-rich dry soil patches as a critical strategy that enabled nutrient capture. We observed nocturnal rewetting of the nutrient-rich but dry soil zone (10 % water and 100 % nutrients) but not in the nutrient-free and dry zone of the control experiment (90 % water and 100 % nutrients). We interpreted the rewetting as the transfer of water from the wet to dry zones through roots, a process commonly known as hydraulic redistribution (HR). The occurrence of HR likely prevents the nutrient-rich soil from drying due to permanent wilting and the subsequent decline of root functions. Sustaining rhizosphere wetness is also likely to increase nutrient mobility and uptake. Lack of HR in the absence of nutrients suggests that HR is not entirely a passive, water-potential-gradient driven flow. The density and size of root hairs appeared to be higher (qualitative observation) in the nutrient-rich and dry compartments than in the nutrient-free and dry compartments. We also observed organic coating on sand grains in the rhizosphere of the nutrient-rich and dry compartments. The observations are consistent with prior observations that root hairs and rhizodeposition aid rhizosphere wetting. These findings were synthesized in a conceptual model that explains how plants of dry regions may be adapted to mismatched resources. This study also suggests that separating the bulk of applied nutrients from the frequently irrigated soil region can increase nutrient use efficiency and curtail water pollution from intensive agricultural systems.</p>
first_indexed 2024-12-23T04:23:56Z
format Article
id doaj.art-b69213c3c3f14bb384e335e12616d0b6
institution Directory Open Access Journal
issn 1726-4170
1726-4189
language English
last_indexed 2024-12-23T04:23:56Z
publishDate 2020-12-01
publisher Copernicus Publications
record_format Article
series Biogeosciences
spelling doaj.art-b69213c3c3f14bb384e335e12616d0b62022-12-21T18:00:11ZengCopernicus PublicationsBiogeosciences1726-41701726-41892020-12-01176377639210.5194/bg-17-6377-2020Root uptake under mismatched distributions of water and nutrients in the root zoneJ. Yan0N. A. Bogie1T. A. Ghezzehei2Life and Environmental Sciences Department, University of California, Merced, CA, 95343, USAGeology Department, San Jose State University, San Jose, CA, 95192, USALife and Environmental Sciences Department, University of California, Merced, CA, 95343, USA<p>Most plants derive their water and nutrient needs from soils where the resources are often scarce, patchy, and ephemeral. It is not uncommon for plant roots to encounter mismatched patches of water-rich and nutrient-rich regions in natural environments. Such an uneven distribution of resources necessitates plant reliance on strategies for exploring and acquiring nutrients from relatively dry patches. We conducted a laboratory study that elucidates the biophysical mechanisms that enable this adaptation. The roots of tomato (<i>Solanum lycopersicum</i>) seedlings were laterally split and grown in two adjacent, hydraulically disconnected pots, which permitted precise control of water and nutrient applications to each compartment. We observed that the physical separation of water-rich and nutrient-rich compartments (one received 90 % water and 0 % nutrients and the other received 10 % water and 100 % nutrients) does not significantly stunt plant growth and productivity compared to two control treatments (control 1: 90 % water and 100 % nutrients versus 10 % water and 0 % nutrients; control 2: 50 % water and 50 % nutrients in each compartment). Specifically, we showed that soil dryness does not reduce nutrient uptake, vegetative growth, flowering, and fruiting compared to control treatments. We identified localized root proliferation in nutrient-rich dry soil patches as a critical strategy that enabled nutrient capture. We observed nocturnal rewetting of the nutrient-rich but dry soil zone (10 % water and 100 % nutrients) but not in the nutrient-free and dry zone of the control experiment (90 % water and 100 % nutrients). We interpreted the rewetting as the transfer of water from the wet to dry zones through roots, a process commonly known as hydraulic redistribution (HR). The occurrence of HR likely prevents the nutrient-rich soil from drying due to permanent wilting and the subsequent decline of root functions. Sustaining rhizosphere wetness is also likely to increase nutrient mobility and uptake. Lack of HR in the absence of nutrients suggests that HR is not entirely a passive, water-potential-gradient driven flow. The density and size of root hairs appeared to be higher (qualitative observation) in the nutrient-rich and dry compartments than in the nutrient-free and dry compartments. We also observed organic coating on sand grains in the rhizosphere of the nutrient-rich and dry compartments. The observations are consistent with prior observations that root hairs and rhizodeposition aid rhizosphere wetting. These findings were synthesized in a conceptual model that explains how plants of dry regions may be adapted to mismatched resources. This study also suggests that separating the bulk of applied nutrients from the frequently irrigated soil region can increase nutrient use efficiency and curtail water pollution from intensive agricultural systems.</p>https://bg.copernicus.org/articles/17/6377/2020/bg-17-6377-2020.pdf
spellingShingle J. Yan
N. A. Bogie
T. A. Ghezzehei
Root uptake under mismatched distributions of water and nutrients in the root zone
Biogeosciences
title Root uptake under mismatched distributions of water and nutrients in the root zone
title_full Root uptake under mismatched distributions of water and nutrients in the root zone
title_fullStr Root uptake under mismatched distributions of water and nutrients in the root zone
title_full_unstemmed Root uptake under mismatched distributions of water and nutrients in the root zone
title_short Root uptake under mismatched distributions of water and nutrients in the root zone
title_sort root uptake under mismatched distributions of water and nutrients in the root zone
url https://bg.copernicus.org/articles/17/6377/2020/bg-17-6377-2020.pdf
work_keys_str_mv AT jyan rootuptakeundermismatcheddistributionsofwaterandnutrientsintherootzone
AT nabogie rootuptakeundermismatcheddistributionsofwaterandnutrientsintherootzone
AT taghezzehei rootuptakeundermismatcheddistributionsofwaterandnutrientsintherootzone