The Sap Flow in the Peduncle of the Mango (Mangifera indica L.) Inflorescence as Measured by the Stem Heat Balance Method

Abstract

The transpired mass flow of water from the inflorescence was monitored continuously and compared with the flow in the whole shoot attached to the inflorescence by the stem heat balance method. The transpiration was compared with the chamber method. The stem heat balance method is able to continuously measure the intact sap flow of water. Modified sap flow gauges were adapted to obtain precise measurements of minute fluctuations in the flow. The stem sap flow fluctuated with the solar radiation, reaching a maximum at midday. The flow was also affected by the saturation deficit. At midday, a sap flow rate was 60 g · h−1 at the shoot base (11.5 mm in diam.); the shoot subtended 55 leaves between the shoot base and the terminal inflorescence. At the peduncle of the inflorescence, the maximum sap flow rate occurred during the morning. Subsequently, the flow tended to decrease gradually and steadily, hardly affected by the solar radiation and the saturation deficit. An entire inflorescence with a peduncle diameter of 11.2 mm exhibited a maximum transpiration rate of 15 g · h−1 during late morning. The daily water consumption of the inflorescence was estimated to be 130 g, representing 22% of the water consumption by the entire shoot. The chamber method indicated similar results as the stem heat balance method.