Boron (B) is an essential micronutr

Boron (B) is an essential micronutrient for plants. Its uptake, transport, and function in plants appearto be dependent on the formation of B complexes with sugars, such as sorbitol in phloem sap (Fig. 1)and a specific dimerised form of pectin in growing cell walls. Yokota and Konishi (1999) studied theeffect of various exogenously supplied sugars including sucrose, glucose, and fructose on promotionof pollen tube growth by formation of sugar-borate complexes. Pollens were cultivated at differentconcentrations of B for 20 hours. Effect of sugars on the pH of the media is shown in Table 1, and thelength of pollen tubes incubated with the various sugars is shown in Fig. 2.