Passage VI

Wheat growth is negatively affected by higher-than-normal salt (NaCl) concentrations in the soil. Scientists investigated whether the negative effects are countered by adding to the soil either a species of bacteria (Species R) or a mixture of proteins from marine algae (PMA).

Study 1

First, 240 identical 2 L pots were each filled with 1.5 kg of a certain soil. Next, 5 wheat seeds were planted in each pot, and the pots were divided equally into 4 groups (Groups 1−4). Then, all the pots in each group received 1 of 4 treatments (see Table 1).

After treatment, each pot was irrigated once every 3 days with either 0.5 L of H₂O only (Group 1) or 0.5 L of H₂O containing 9.3 g/L of NaCl (Groups 2−4). The average number of seeds germinated per pot was then determined for each group at 3, 5, 7, and 9 days after treatment (see Table 2).

Study 2

An additional 240 of the 2 L pots were prepared, treated, and irrigated as in Study 1. Nine days after treatment, all but 1 seedling were removed from each of the pots that had multiple seedlings. Each pot was then irrigated as in Study 1 for an additional 75 days. The average plant height was then determined for each group (see Figure 1).

Table 2 and Figure 1 adapted from Elhafid Nabti et al., “Restoration of Growth of Durum Wheat (Triticum durum var. waha) Under Saline Conditions Due to Inoculation with the Rhizosphere Bacterium Azospirillum brasilense NH and Extracts of the Marine Alga Ulva lactuca.” ©2010 by Springer Science and Business Media, LLC.