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Full-Text Articles in Life Sciences
Allocation Tradeoffs Among Chaparral Shrub Seedlings With Different Life History Types (Rhamnaceae), R. Pratt, A. Jacobsen, J. Hernandez, F. Ewers, Gretchen North, S. Davis
Allocation Tradeoffs Among Chaparral Shrub Seedlings With Different Life History Types (Rhamnaceae), R. Pratt, A. Jacobsen, J. Hernandez, F. Ewers, Gretchen North, S. Davis
Gretchen North
• Premise of the Study: California chaparral shrub species have different life history types: Nonsprouters (NS) are killed by fi re and persist through a fi re-stimulated seed bank; facultative sprouters (FS) reestablish by a combination of vegetative sprouting and seeding; and obligate sprouters (OS) reestablish exclusively by sprouting. Nonsprouters and FS establish seedlings in opencanopy postfi re environments, whereas OS establish seedlings between fi res in the shady understory. We hypothesized that allocation differences among seedlings of postfi re sprouters and nonsprouters and regeneration niche differences would lead to contrasting patterns in biomass accumulation (NS > FS > OS, in sun; …
Root Contraction Helps Protect The "Living Rock" Cactus Ariocarpus Fissuratus From Lethal High Temperatures When Growing In Rocky Soil, Gretchen North, T.Y. Garrett, C.V. Huynh
Root Contraction Helps Protect The "Living Rock" Cactus Ariocarpus Fissuratus From Lethal High Temperatures When Growing In Rocky Soil, Gretchen North, T.Y. Garrett, C.V. Huynh
Gretchen North
• Premise of the study: We investigated how the “living rock” cactus Ariocarpus fissuratus, like other low-growing desert plants, can endure potentially lethal high temperatures at the soil surface. Specifically, we examined how shoot descent by root contraction in the presence or absence of soil rocks influences shoot temperatures and transpiration. • Methods: Root contraction was identified by measuring shoot descent and anatomical analysis. Temperatures and transpiration were measured for plants at two heights in sandy and rocky soil, and temperature tolerances were determined by vital staining. • Key results: Plants embedded in rocky soil survived an extreme heat episode, …
Structural Implications Of Succulence: Architecture, Anatomy, And Mechanics Of Photosynthetic Stem Succulents, Pachycauls, And Leaf Succulents, Gretchen North, E. Bobich
Structural Implications Of Succulence: Architecture, Anatomy, And Mechanics Of Photosynthetic Stem Succulents, Pachycauls, And Leaf Succulents, Gretchen North, E. Bobich
Gretchen North
No abstract provided.
Plant Hydraulics: New Discoveries In The Pipeline (Meeting Report), R. Pratt, A. Jacobsen, Gretchen North, L. Sack, H. Schenk
Plant Hydraulics: New Discoveries In The Pipeline (Meeting Report), R. Pratt, A. Jacobsen, Gretchen North, L. Sack, H. Schenk
Gretchen North
No abstract provided.
Water Uptake By Older Roots: Evidence From Desert Succulents, Gretchen North, E. Baker
Water Uptake By Older Roots: Evidence From Desert Succulents, Gretchen North, E. Baker
Gretchen North
Desert succulents are renowned for their rapid recovery of shoot function after periods of drought as a result of shoot succulence, root–shoot interactions, and key root properties. Near the base of the shoot, the proximal (generally older) roots appear to play a major role in the rapid uptake and delivery of water, especially after a period of soil drying when the rest of the root system has a lower hydraulic conductance. In all of the cacti, agaves, and yuccas examined to date, hydraulic conductance for the proximal root zone is unexpectedly high. Substantial water uptake by older roots of cacti …
Water Flow In Roots: Structural And Regulatory Features, Gretchen North, C. Peterson
Water Flow In Roots: Structural And Regulatory Features, Gretchen North, C. Peterson
Gretchen North
No abstract provided.
A Long Drink Of Water: How Xylem Changes With Depth, Gretchen North
A Long Drink Of Water: How Xylem Changes With Depth, Gretchen North
Gretchen North
No abstract provided.
Aquaporins Account For Variations In Hydraulic Conductance For Metabolically Active Root Regions Of Agave Deserti In Wet, Dry, And Rewetted Soil, Gretchen North, P. Martre, P. Nobel
Aquaporins Account For Variations In Hydraulic Conductance For Metabolically Active Root Regions Of Agave Deserti In Wet, Dry, And Rewetted Soil, Gretchen North, P. Martre, P. Nobel
Gretchen North
The importance of aquaporins for root hydraulic conductance (LP) was investigated along roots of the desert succulent Agave deserti in wet, dry and rewetted soil. Water channel activity was inferred from HgCl2-induced reductions of LP that were reversible by 2-mercaptoethanol. Under wet conditions, HgCl2 reduced LP for the distal root region by 50% and for the root region near the shoot base by 36% but did not affect LP for the mid-root region. For all root regions, LP decreased by 30–60% during 10 d in drying soil and was not further reduced by HgCl2. After soil rewetting, LP increased to …
Root Deployment And Shoot Growth For Two Desert Species In Response To Soil Rockiness, P. Martre, Gretchen North, E. Bobich, P. Nobel
Root Deployment And Shoot Growth For Two Desert Species In Response To Soil Rockiness, P. Martre, Gretchen North, E. Bobich, P. Nobel
Gretchen North
Soil texture, as well as the presence of rocks, can determine the water status, growth, and distribution of plants in arid environments. The effects of soil rockiness and soil particle size distribution on shoot and root growth, root system size, rooting depth, and water relations were therefore investigated for the Crassulacean acid metabolism leaf succulent Agave deserti and the C4 bunchgrass Pleuraphis rigida after precipitation events during the summer and winter/spring rainfall periods in the northwestern Sonoran Desert. The soils at the field site varied from sandy (<3% rocks by volume) to rocky (up to 35% rocks), with greater …
Plasma Membrane Aquaporins Play A Significant Role During Recovery From Water Deficit, P. Martre, R. Morillon, F. Barrieu, Gretchen North, P. Nobel, M. Chrispeels
Plasma Membrane Aquaporins Play A Significant Role During Recovery From Water Deficit, P. Martre, R. Morillon, F. Barrieu, Gretchen North, P. Nobel, M. Chrispeels
Gretchen North
The role of plasma membrane aquaporins (PIPs) in water relations of Arabidopsis was studied by examining plants with reduced expression of PIP1 and PIP2 aquaporins, produced by crossing two different antisense lines. Compared with controls, the double antisense (dAS) plants had reduced amounts of PIP1 and PIP2 aquaporins, and the osmotic hydraulic conductivity of isolated root and leaf protoplasts was reduced 5- to 30-fold. The dAS plants had a 3-fold decrease in the root hydraulic conductivity expressed on a root dry mass basis, but a compensating 2.5-fold increase in the root to leaf dry mass ratio. The leaf hydraulic conductance …
Hydraulic Conductance And Mercury-Sensitive Water Transport For Roots Of Opuntia Acanthocarpa In Relation To Soil Drying And Rewetting, P. Martre, Gretchen North, P. Nobel
Hydraulic Conductance And Mercury-Sensitive Water Transport For Roots Of Opuntia Acanthocarpa In Relation To Soil Drying And Rewetting, P. Martre, Gretchen North, P. Nobel
Gretchen North
Drought-induced changes in root hydraulic conductance (L P) and mercury-sensitive water transport were examined for distal (immature) and mid-root (mature) regions ofOpuntia acanthocarpa. During 45 d of soil drying,L P decreased by about 67% for distal and mid-root regions. After 8 d in rewetted soil,L P recovered to 60% of its initial value for both regions. Axial xylem hydraulic conductivity was only a minor limiter of L P. Under wet conditions, HgCl2 (50 μM), which is known to block membrane water-transport channels (aquaporins), decreasedL P and the radial hydraulic conductance for the stele (L R, S) of the distal root …
Heterogeneity In Water Availability Alters Cellular Development And Hydraulic Conductivity Along Roots Of A Desert Succulent, Gretchen North, P. Nobel
Heterogeneity In Water Availability Alters Cellular Development And Hydraulic Conductivity Along Roots Of A Desert Succulent, Gretchen North, P. Nobel
Gretchen North
Plants of the desert succulent Agave deserti were grown in partitioned containers to determine whether heterogeneity in soil moisture leads to differences in cellular development and hydraulic conductivity along individual roots. Roots from containers with a dry distal compartment (furthest from the shoot), a wet middle compartment, and a dry proximal compartment had distal regions (including the root tips) that were more suberized and lignified in the endodermis and adjacent cell layers than were root regions from the wet middle compartment. Proximal root regions about 40 mm from the succulent shoot base were also relatively unsuberized, suggesting that both external …
Root Growth, Developmental Changes In The Apex, And Hydraulic Conductivity For Opuntia Ficus-Indica During Drought, J. Dubrovsky, Gretchen North, P. Nobel
Root Growth, Developmental Changes In The Apex, And Hydraulic Conductivity For Opuntia Ficus-Indica During Drought, J. Dubrovsky, Gretchen North, P. Nobel
Gretchen North
Developmental changes in the root apex and accompanying changes in lateral root growth and root hydraulic conductivity were examined for Opuntia ficus-indica (L.) Miller during rapid drying, as occurs for roots near the soil surface, and more gradual drying, as occurs in deeper soil layers. During 7 d of rapid drying (in containers with a 3-cm depth of vermiculite), the rate of root growth decreased sharply and most root apices died; such a determinate pattern of root growth was not due to meristem exhaustion but rather to meristem mortality after 3 d of drying. The length of the meristem, the …
Root-Soil Contact For The Desert Succulent Agave Deserti Engelm. In Wet And Drying Soil, Gretchen North, P. Nobel
Root-Soil Contact For The Desert Succulent Agave Deserti Engelm. In Wet And Drying Soil, Gretchen North, P. Nobel
Gretchen North
To investigate the extent and size of root-soil air gaps that develop during soil drying, resin casts of roots of the desert succulent Agave deserti Engelm. were made in situ for container-grown plants and in the field. Plants that were droughted in containers for 7 and 14 d had 24 and 34% root shrinkage, respectively, leading to root-soil air gaps that would reduce the hydraulic conductivity at the root-soil interface by a factor of about 5. When containers were vibrated during drought, root-soil air gaps were greatly diminished, and the predicted conductivity at the interface was similar to that of …
Features Of Roots Of Cam Plants, P. Nobel, Gretchen North
Features Of Roots Of Cam Plants, P. Nobel, Gretchen North
Gretchen North
No abstract provided.
Radial Hydraulic Conductivity Of Individual Root Tissues Of Opuntia Ficus-Indica (L.) Miller As Soil Moisture Varies, Gretchen North, P. Nobel
Radial Hydraulic Conductivity Of Individual Root Tissues Of Opuntia Ficus-Indica (L.) Miller As Soil Moisture Varies, Gretchen North, P. Nobel
Gretchen North
The constraints on water uptake imposed by individual root tissues were examined for Opuntia ®cus-indica under wet, drying, and rewetted soil conditions. Root hydraulic conductivity (L P ) and axial conductance (K h ) were measured for intact root segments from the distal region with an endodermis and from midroot with a periderm; L P was then measured for each segment with successive tissues removed by dissection. Radial conductivity (L R ) was calculated from L P and K h for the intact segment and for the individual tissues by considering the tissue conductivities in series. Under wet conditions, L …
Hydraulic Conductivity Of Concentric Root Tissues Of Agave Deserti Englem. Under Wet And Drying Conditions, Gretchen North, P. Nobel
Hydraulic Conductivity Of Concentric Root Tissues Of Agave Deserti Englem. Under Wet And Drying Conditions, Gretchen North, P. Nobel
Gretchen North
Water moves from the root surface to the root xylem through a series of tissues, each with properties that influence the root radial hydraulic conductivity (LR). To determine LR for intact roots, root hydraulic conductivity (LP) and axial (xylem) conductance (Kh) were measured for root segments of the desert succulent Agave deserti Engelm. As layers were successively removed, LR was calculated for each layer by considering the conductivities in series. For the distal root region, no single tissue limited LR under wet conditions, although the suberized exodermis and sclerenchyma/endodermis were more limiting per cross-sectional area of the root than were …
Water Potentials For Developing Cladodes And Fruits Of A Succulent Plant, Including Xylem-Versus-Phloem Implications For Water Movement, P. Nobel, J. Andrade, N. Wang, Gretchen North
Water Potentials For Developing Cladodes And Fruits Of A Succulent Plant, Including Xylem-Versus-Phloem Implications For Water Movement, P. Nobel, J. Andrade, N. Wang, Gretchen North
Gretchen North
Developing cladodes had lower water potentials and developing fruits had higher water potentials than the underlying cladodes of the widely cultivated prickly pear cactus, Opuntia ficus-indica. The 0.06 MPa lower value in 4-week-old daughter cladodes indicated a typical water potential gradient from the underlying clad-ode along the xylem of −0.2 MPa m−1; the 0.17 MPa higher value in 4-week-old fruits, which decreased to 0.07 MPa by 10 weeks, implicated the phloem as their supplier of water. The phloem sap of the underlying cladodes had an osmotic pressure of only 0.90 to 0.98 MPa, so the phloem could supply a relatively …
Changes In Root Hydraulic Conductivity For Two Tropical Epiphytic Cacti As Soil Moisture Varies, Gretchen North, P. Nobel
Changes In Root Hydraulic Conductivity For Two Tropical Epiphytic Cacti As Soil Moisture Varies, Gretchen North, P. Nobel
Gretchen North
The tropical epiphytic cacti Epiphyllum phyllanthus and Rhipsalis baccifera experience extreme variations in soil moisture due to limited soil volumes and episodic rainfalls. To examine possible root rectification, whereby water uptake from a wet soil occurs readily but water loss to a dry soil is minimal, responses of root hydraulic conductivity (Lp) to soil drying and rewetting were investigated along with the underlying anatomical changes. After 30 d of soil drying, Lp decreased 50%-70% for roots of both species, primarily because increased suberization of the periderm reduced radial conductivity. Sheaths composed of soil particles, root hairs, and mucilage covered young …
Cladode Development For Opuntia Ficus-Indica (Cactaceae) Under Current And Doubled Co2 Concentrations, Gretchen North, T.L. Moore, P.S. Nobel
Cladode Development For Opuntia Ficus-Indica (Cactaceae) Under Current And Doubled Co2 Concentrations, Gretchen North, T.L. Moore, P.S. Nobel
Gretchen North
Morphological and anatomical changes for first-order daughter cladodes (flattened stem segments) of a prickly pear cactus, Opuntia ficus-indica, were monitored to determine the effects of a doubled atmospheric CO2 concentration on their development and mature form. For daughter cladodes developing in controlled environment chambers for 60 d, maximal elongation rates were similar under a photosynthetic photon flux density (PPFD) of 6 mol m-2 d-1 and a CO2 concentration of 370 μl liter-1, an increased PPFD (10 mol m-2 d-1), and an increased PPFD and a doubled CO2 concentration. These maximal rates, however, occurred at 20, 15, and 12 d, respectively. …
Changes In Hydraulic Conductivity And Anatomy Caused By Drying And Rewetting Roots Of Agave Deserti (Agavaceae), Gretchen North, P. Nobel
Changes In Hydraulic Conductivity And Anatomy Caused By Drying And Rewetting Roots Of Agave Deserti (Agavaceae), Gretchen North, P. Nobel
Gretchen North
Concurrent determinations of changes in hydraulic conductivity and tissue anatomy were made for roots of Agave deserti excised during drying and following rewetting in soil. At 30 d of drought, hydraulic conductivity had declined less than twofold for older nodal roots, tenfold for young nodal roots, and more than 20-fold for lateral roots ("rain roots" occurring as branches on the nodal roots). These decreases were consistent with increases in cortical lacunae caused by cell shrinkage and collapse. Similarly, reduction of lacunae in response to rewetting after 7 d of drought corresponded to levels of recovery in hydraulic conductivity, with young …