Abstract Detail

Ecophysiology

Ortiz, Hector [1], Stewart, J. Ryan [2], Park, Pilman [3], Hadfield, Robert [4], Squire, Madison [5].

Thermal Properties of Hohokam Rock-Piles Boost Agave Photosynthesis: Assessment of Agave murpheyi and Agave americana in Rock-Piles.

The pre-Columbian indigenous group, Hohokam, used rock-piles to cultivate agaves in Arizona. Rock-piles acted as mulch to retain soil moisture and catch rainfall runoff at hill slopes. These rock-piles were the main approach for cultivating drought tolerant agaves. Agave murpheyi and Agave americana are among the agaves in the region cultivated by the Hohokam. Hohokam Agave, or Agave murpheyi, has been reported as endemic at archaeologic sites in Arizona. In addition, Agave americana remnants have been reported at Hohokam rock-pile fields. Because these two Agave species have the potential to produce large amounts of edible biomass in limited water conditions, evidence suggests that they were introduced synanthropically to Arizona. However, few studies have addressed how insulation properties of rock-piles likely contributed to bolster Agave drought tolerance, CAM metabolism, and productivity of these two Hohokam agaves. We hypothesized that soil moisture and temperature in rock-piles affect CAM metabolism efficiency by increasing nocturnal CO₂ gas exchange rates of Agave murpheyi and Agave americana. In a field and lab-based experiment using 3-year-old Agave americana and Agave murpheyi plants growing in rock-piles (circular shape, 50-70 cm diameter) in a sandy-loam soil, we compared nocturnal CO₂ gas exchange rates of agaves in exposed soil and rock-piles. Real-time nocturnal CO₂ gas exchange measurements were made using a portable infrared photosynthesis and CO₂ gas analyzer (LICOR-LI-6400XT). The equipment was adapted to sample CO₂ gas exchange at leaf level during overnight measurements. Thermal images from rock piles and exposed soil were collected using an infrared thermometer (FLIR-E5). Soil water potential was measured in the lab from soil samples collected at rock piles and exposed soil using a water potential meter (WP4C). Preliminary results indicate a delay of the initial CO₂ gas exchange of agaves growing in rock-piles. Differences in CO₂ exchange rates may be due to high soil moisture and cool soil temperatures during the day, but warmer temperatures below rocks at night. Rock-piles reduce soil evapotranspiration and daily temperatures below rocks, which may be beneficial to the metabolic response of agaves by reducing drought and heat stress.
Keywords: Nocturnal CO₂ gas exchange, Agave murpheyi, Agave americana, photosynthesis, rock-piles.

1 - Brigham Young University, Plant and Wildlife Sciences, Life Science Building (LSB), 5043B, Provo, Utah, 84602, USA
2 - Brigham Young University, Pland and Wildlife Sciences, Life Science Building (LSB), 2124, Provo, Utah, 84602, USA
3 - National Institute of Horticultural & Herbal Science, RDA, Horticulture, Iseo-myeon, Iseo-myeon, Jeollabuk-do, KOR
4 - Brigham Young University, Chemistry/Biochemestry, Life Science Building (LSB), Lab 5016, Provo, Utah, 84602, USA
5 - Brigham Young University, Biology, Life Science Building (LSB), Lab 5016, Provo, Utah, 84602, USA

Keywords:
Agave
gas exchange
photosynthesis
rock-piles.

Presentation Type: Poster
Session: P, Ecophysiology Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPE012
Abstract ID:994
Candidate for Awards:Physiological Section Best poster presentation,Physiological Section Physiological Section Li-COR Prize