WATER RELATIONS OF MYCORRHIZAL AND PHOSPHORUS-FERTILIZED NON-MYCORRHIZAL CITRUS UNDER DROUGHT STRESS.

Area of Science:

• Plant Physiology
• Soil Microbiology
• Agronomy

Background:

• Citrus production is often limited by water availability and soil phosphorus.
• Vesicular-arbuscular mycorrhizal (VAM) fungi can enhance plant nutrient uptake and drought tolerance.
• The role of VAM in citrus water relations under drought stress requires further investigation.

Purpose of the Study:

• To investigate the effect of VAM inoculation on the water relations of citrus rootstocks under drought stress.
• To compare the performance of VAM and non-mycorrhizal (NM) citrus seedlings under well-watered and drought conditions.

Main Methods:

• Citrus rootstock seedlings (Carrizo citrange and sour orange) were grown in low-phosphorus soil and inoculated with Glomus intraradices (VAM) or fertilized with soluble phosphorus (NM).
• Seedlings were subjected to well-watered or drought-stress cycles.
• Whole plant transpiration, leaf water status, and root hydraulic conductivity were measured.

Main Results:

• VAM and NM seedlings showed comparable size, phosphorus sufficiency, and growth rates under well-watered and drought conditions.
• Under drought, VAM plants maintained similar transpiration rates and leaf water potentials to NM plants.
• Mycorrhiza significantly reduced root hydraulic conductivity in Carrizo citrange (66%) and sour orange (49%) during drought and recovery.

Conclusions:

• The data do not support the hypothesis that VAM significantly enhances water relations in citrus under the studied drought conditions.
• Mycorrhizal colonization negatively impacted root hydraulic conductivity in citrus rootstocks during drought stress.