Effects of Quantity and Temperature of Storage Roots on the Elongation Rates of Asparagus Spears

Abstract

Effects of quantity and temperature of storage roots on the elongation rates of spears were studied using 1-year-old asparagus.
1. The elongation rates were affected by the sizes of crowns. The spears from normal-sized crowns grew exponentially, but those from small-sized crowns grew almost linearly.
2. The spears grew exponentially while storage materials were plentiful in storage roots, but grew linearly and then parabolically as the materials were exhausted.
3. The elongation rates of spears were influenced by root temperature. Rates were highest at 20 or 25°C. The more the temperature deviated from these levels, the more the rates decreased. But spears grew exponentially even at aroot temperature of 5°C. It was probable that root temperature affected the elongation growth of spears not directly, but indirectly by modifying the temperature of spear and/or rhizome.
4. The temperature treatments of buds for about 2.5 days before sprouting did not influence the subsequent elongation growth of spears.
5. The ratios of water-weight: dry-weight in spears grown at root temperature of 10°C were lower than those at 15 or 20°C.
It was suggested that as long as available storage materials were plentiful, spear growth was mostly influenced by spear and/or rhizome activities rather than by root activity.