Root Elongation in Various Agronomic Crops by the Plant Growth Promoting Rhizobacterium Pseudomonas Putida Gr12–2

Abstract

Seeds of canola, lettuce, tomato, barley, wheat, and oats were inoculated with either the wild-type plant growth promoting rhizobacterium (PGPR), Pseudomonas putida GR12–2, or the mutant P. putida GR 12–2lacd68 (deficient in the activity of the enzyme 1-aminocyclopropane-1-carboxylate deaminase) alone and in conjunction with either an inhibitor of ethylene biosynthesis, L-α-(aminoethoxyvinyl)-glycine (AVG), or the chemical ethylene generator, (2-chloroethyl) phosphonic acid (ethophon). For the different treatments, variations in root length under gnotobiotic conditions were compared. Canola, lettuce, tomato, and wheat responded to all of the treatments in a similar manner: The root lengths increased when seeds were treated with P. putida GR 12–2 and/or AVG but not with the mutant strain, in comparison with a MgSO4 control treatment, while the ethophon treatment inhibited root elongation. With barley and oat, none of the treatments had any effect on root lengths; however, when the ethophon concentration was increased, root elongation of these two plants was also inhibited. These observations are consistent with a model in which promotion of root growth by P. putida GR 12–2 is a consequence of inhibition of ethylene production within the developing seedling.

Effect of organic fertilization on yield and quality of rosemary (Rosmarinus officinalis L.) essential oil

“…However Abdel et al (2014) reports how microbial colonization by A. chroococcum is significantly affected by factors like nitrogenous fertilization, plant growth state and soil moisture content, among others. For P. flourescens it is reported how its application increases the roots elongation and the aerial component of canola, lettuce and tomato (Hall et al, 1996;Dadrasan et al, 2015), however the results of this research allow to conclude that for the R. officinalis var. Israeli species at this agroclimatic and edaphic conditions, the treatments did not contribute to increase the plant height.…”

New advances in plant growth-promoting rhizobacteria for bioremediation

“…Ethylene is important for plant growth (Deikman, 1997), while excessive ethylene promoted by stresses can depress growth (Morgan and Drew, 1997). PGPR have a positive effect on plant growth by consuming amino-cyclopropane carboxylic acid (ACC), the immediate precursor to ethylene, through synthesis of 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) to decrease the ethylene production in stressed plants (Hall et al, 1996;Reed and Glick, 2005;Safronova et al, 2006).…”

Transformation of Azospirillum brasilense Cd with an ACC Deaminase Gene from Enterobacter cloacae UW4 Fused to the Tet r Gene Promoter Improves Its Fitness and Plant Growth Promoting Ability

“…The bacteria accomplish this by breaking down the immediate precursor of ethylene, 1-aminocyclopropane 1-carboxylate (ACC), by ACC deaminase [17][18][19]22].…”

“…Some of the effects that result in lower ethylene levels due to ACC deaminase activity in plant growth-promoting bacteria are reduction in the extent of ethylene inhibition of plant seedling root elongation [15,18,22] and amelioration of the inhibitory effects of stress ethylene on plant growth caused by the presence of heavy metals [12], phytopathogens [37], and flooding [21].…”

“…Expression of this construct in A. brasilense Cd improves the fitness of the bacterium and its ability to promote plant growth, compared to the construct containing acdS under the control of the lac promoter. We chose tomato plants as the host plant for these studies because of the high sensitivity of tomato plants to ethylene [22].…”