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United States Department of Agriculture

Agricultural Research Service

Title: Physiological response of beans inoculated with AM fungi under short-term flooding

Authors
item Sah, Seema - FLORIDA INTL UNIV
item Reed, Stewart
item Jayachandran, Krish - FLORIDA INTL UNIV
item Hartley, Anne - FLORIDA INTL UNIV
item Fisher, Jack - FAIRCHILD TROPICAL BOT

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 20, 2006
Publication Date: N/A

Interpretive Summary: Florida ranks first in snap bean production in the United States with close to 50% of the total production. Flooding is one of the serious problems facing crop production in south Florida. Arbuscular mycorrhizal fungi are well known to increase nutrient uptake in wet and dry conditions, and enhance secretion of growth hormone to increase plant biomass and yield. However, there is still much to learn about the effects of flooding and mycorrhizal colonization on snap bean growth. An experiment was conducted to determine the effects of flooding and mycorrhizal colonization on plant photosynthesis and nitrogen (N) and phosphorus (P) uptake. Snap bean plants were subjected to either flooded or normal watering conditions and were inoculated with one of four different mycorrhizal suites. Pots were arranged in a random order in a greenhouse. Plants were grown in a 9:1 ratio of steamed sand and compost. Flood treatments were imposed for eight hours every seventh day by emerging pots in water to 1 cm above the soil surface. Flood treatments began at 20 days after planting (DAP) and plants were harvested 45 DAP. Photosynthesis (net carbon dioxide assimilation), transpiration (net evaporation of water from the leaf surface) and stomatal resistance (resistance to water flow through the stomates) were measured 24 h after each flood treatment. Shoot and root biomass, total carbon, total nitrogen and total phosphorus were measured at harvest. Experimental results revealed that short term flooding did not affect plant growth. Flooding did not affect survival of mycorrhizal colonies established in plant roots before the onset of flood treatments. Flooding and mycorrhizal inoculation had different effects on carbon (C), N, and P partitioning within the plant. Flooding decreased dry weight, total plant C and the dry weight produced per unit N and P. Mycorrhizal inoculation increased dry weight, shoot C, shoot N and the dry weight produced per unit P. However, mycorrhizal inoculation reduced the dry weight produced per unit N. While there was no difference in C assimilation from photosynthesis, mycorrhizal plants had a higher total plant C than uninoculated ones. Carbon dioxide uptake in photosynthesis was consistently lowest in the flooded, mycorrhizal plants but the difference was not significant. However, we could not conclude mycorrhizae act as a C drain in plants under stress.

Technical Abstract: Florida ranks first in snap bean production in the United States with close to 50% of the total production. Flooding is one of the serious problems facing crop production in south Florida. Arbuscular mycorrhizal fungi are well known to increase nutrient uptake in wet and dry conditions, and enhance secretion of growth hormone to increase plant biomass and yield. However, there is still much to learn about the effects of flooding and mycorrhizal colonization on snap bean growth. A greenhouse experiment was conducted to determine the effects of flooding and mycorrhizal colonization on plant photosynthesis and nitrogen (N) and phosphorus (P) uptake. A completely randomized design with two different levels of flooding and four levels of mycorrhizal inoculation was set up in a greenhouse. Plants were grown in a 9:1 ratio of steamed sand and compost. Flood treatments were imposed for eight hours every seventh day by emerging pots in water to 1 cm above the soil surface. Flood treatments began at either 13 or 20 days after planting (DAP) and plants were harvested 35 DAP or 45 DAP. Photosynthesis, transpiration and stomatal resistence were measured 24 h after each flood treatment. Shoot and root biomass, total carbon, total nitrogen and total phosphorus were measured at harvest. Analysis of variance (ANOVA) was used to determine the differences between treatments. Experimental results revealed that short term flooding did not affect plant growth. Flooding did not affect survival of mycorrhizal colonies established in plant roots before the onset of flood treatments. Flooding and mycorrhizal inoculation had different effects on C, N, and P partitioning. Flooding decreased dry weight, total plant C and the dry weight produced per unit N and P. Mycorrhizal inoculation increased dry weight, shoot C, shoot N and the dry weight produced per unit P. However, mycorrhizal inoculation reduced the dry weight produced per unit N. While there was no difference in C assimilation from photosynthesis, mycorrhizal plants had a higher total plant C than uninoculated ones. Carbon dioxide uptake in photosynthesis was consistently lowest in the flooded, mycorrhizal plants but the difference was not significant. However, we could not conclude mycorrhizae act as a C drain in plants under stress.

Last Modified: 7/25/2014
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