IAA Distribution in Etiolated Spears of Asparagus

Abstract

Asparagus (Asparagus officinalis L.) spears can grow extraordinarily quickly (Kojima et al., 1993a). Elucidation of a mechanism involved in the ability of asparagus spears to grow so quickly may afford a clue for the improvement of cultivations, not only in asparagus, but also in other products. Kojima et al. (1993a) reported that growing spears had a declining gradient of abscisic acid (ABA) concentration from the tip toward the butt and suggested that ABA was involved in mobilizing carbohydrate reserves for spear growth. However, Patrick and Steains ( 1987) reported that indole-3-acetic acid (IAA) also had a role in promoting assimilate translocation. IAA has been considered to promote cell elongation (Goldsmith, 1977). Thus, IAA may also influence spear growth rate. Green ‘Jersey Giant’ asparagus spears had higher levels of IAA than white asparagus (Makus and Guinn, 1992). However, to our knowledge, no one has reported IAA distribution in asparagus spears. In Mar. 1990, 1-year-old crowns of ‘Mary Washington 500W’ were planted 2 cm deep in a sandy loam soil in 2-liter pots and placed in a greenhouse at the Hiroshima Prefectural Agricultural Experimental Station (Hara, Japan). In Jan. 1991, the 2-year-old crowns sprouted in a dark room at 20 to 23C. Spears sprouted and grown in darkness can be regarded as being similar to white asparagus. Samples were collected from the following spear height ranges (in millimeters): 35–50, 51-100, 101-150, 151-200, and 300-400. When spear heights ranged from 35 to 50 mm, six spears were collected. When heights were >50 mm, 12 spears were collected. Sampled spears were cut into four sections. The tip region consisted of 0 to 15and 15-to 35-mm segments. Spears > 50 mm long (measured from the tip) were cut below the tip region into two additional lengths in a 1 : 2 ratio and