Avner Silber

ISHS XIV International Protea Research Symposium Evolutionary adaptation of plants to phosphorus deficiency: the multifaceted role of cluster roots

We assessed the effects of N concentration in the irrigation water on nutrient uptake and distribution in leaves and fruit of mango cv. Keitt grown in a lysimeter for four years. We applied three treatments: N1 – no N fertilization (less than 2 mg/L in the tap water); N2 – 10 mg/L N; N3 – 20 mg/L N. Deficient N conditions (N1) generated low vegetative yield, high fruit:leaf ratio, high photosynthetic activity, high leaf P and K concentrations, and high sugar content along with low acidity in the fruit. Excess N concentration (N3) induced vegetative growth, and reduced fruit yield and gas-exchange characteristics. The calculated annual nitrogen uptake heavily depended on the nitrogen supply (N1-26 g/tree; N2-196 g/tree; N3- 185 g/tree). Fruits were the major N sink being 0.82, 0.26 and 0.05 from the total annual N supplied. The N quantities accumulated in N1 fruits during the reproductive season (May-August), were above the N quantities supplied via fertigation, suggesting that N reserve in the vegetative tissues supplied the fruit’s high N demand. The finding shows the importance of adequate nitrogen supply to mango trees and the dangers of excessive fertilization.

ISHS IV International Protea Working Group Symposium EFFECTS OF PHOSPHORUS AND NITROGEN CONCENTRATION ON LEUCADENDRON ‘SAFARI SUNSET’ DEVELOPMENT