Plant Material
Cuttings of poplar (Populus deltoides Barr. S7c8 East Texas day
neutral clone; and Populus trichocarpa BESC2074639) were grown at
the University of New Mexico (35.0843° N, 106.6198° W, 1587 m a.s.l.) at
18.3 to 21.1/15.6 to 21.1 °C day/night temperature in a rooftop
greenhouse, and bell pepper (Capsicum annuum var. V6220
California Wonder Bell Pepper) were grown in an indoor greenhouse at
22/16 °C day/night temperature with 12/12 day/night photoperiod
maintained using a SPYDR 600 LED lighting system (BML Horticulture,
Austin, TX, USA) at a minimum intensity of 170 μmol
m-2 s-1 (maximum light intensity of
~720 μmol m-2 s-1including the natural light in the indoor greenhouse). Populus
deltoides were grown in 28 L pots and were ~2 years old
during measurements, Populus trichocarpa were grown in 7 L pots
and were <6 months old during measurements, and Capsicum
annuum were grown in 28 L pots. All three greenhouse species were grown
in Metro-Mix 300 potting soil (Sun Gro Horticulture, Seba Beach, AB,
Canada), and were fertilized twice weekly with Peters 20-20-20 (Scotts
Miracle-Gro, Marysville, OH, USA) and once weekly with chelated liquid
iron (Ferti-Lome, Bonham, TX, USA). USDA-certified organic Granny Smith
apple trees (Malus domestica Borkh.) were grown in Los Lunas, NM
at the New Mexico State University Agricultural Science Center (34.6007°
N, 103.2139° W, 1793 m a.s.l., MAP: 241 mm, MAT: 13.9 °C, Soil: loam,
Slope: 0 – 1%; USDA, 2018). Showy milkweed (Asclepias
speciosa ), mature Chinquapin oak (Quercus muehlenbergii ), and
Queen Elizabeth rose (Rosa grandiflora ) were grown at the ABQ
BioPark Botanic Garden in Albuquerque, NM (35.0933° N 106.6813° W, 1587
m a.s.l., MAP: 203 mm, MAT: 17.5 °C, Soil: fine sandy loam, Slope: 0 –
1%, USDA, 2018). Mature ponderosa pine (Pinus ponderosa ) were
measured at Las Huertas Upper Picnic Grounds in Cibola National Forest,
Sandoval County, NM (35.235458° N, 106.413012° W, 2316 m a.s.l., MAP:
546 mm, MAT: 6.1 °C, Soil: stony loam, Slope: 35 – 70%, USDA, 2018).
Measurements were made on October 26th, 2017, and
observed sunrise/sunset was 8:30am and 5:00pm due to the location of the
measurement site in a canyon with mountains on all sides. Mature Deodar
cedar (Cedrus deodar , sample size limited to 4 available trees)
and mature ginkgo (Ginkgo biloba , sample size limited to 3
available trees) from the University of New Mexico Arboretum (35.0843°
N, 106.6198° W, 1587 m a.s.l., MAP: 203 mm, MAT: 17.5 °C, Soil: cut and
fill, USDA, 2018) were measured on August 24th, 2018.
Unless stated above, sample size for each species was one leaf (or
branch for needleleaf species) from each of six individuals. Note: the
timing of measurements and sample size varied depending on access to
equipment, facilities and biological material (especially for field
measurements), however this should not affect the presence or absence of
diurnal changes in Vcmax .