3’-(Phenyl alkynyl) Analogs of Abscisic Acid: Two Step Synthesis of Potent ABA Antagonists

We report here the synthesis and biological testing of 3’-phenyl alkynyl abscisic ABA analogs, a new class of potent ABA antagonists. These ABA analogs incorporate a rigid framework of eight...

Conformationally restricted 3′-modified ABA analogs for controlling ABA receptors

(+)-PAO4 is a conformationally restricted analog of AS6 that was synthesized to improve the affinity for PYL proteins.

Evaluation of Abscisic Acid Analogs as Holding Agents for Bedding Plant Seedlings

The marketing period of nursery-raised bedding plant seedlings is limited by the loss of aesthetic quality associated with undesirable growth and/or excess moisture loss during storage and handling. Long-lasting synthetic analogs of abscisic acid (ABA) (8′-methylene ABA methyl ester and 8′-acetylene ABA methyl ester) were evaluated for their potential use in controlling growth and extending the marketing period of seedlings of tomato (Lycopersicon esculentum), snapdragon (Antirrhinum majus), and nasturtium (Tropelaum majus). ABA analogs, applied as root-dips, slowed moisture use and reduced seedling growth in a dosage-dependent manner with no significant phytotoxic effects over the short term. The nature and duration of the responses of the three test crops to the ABA analog treatments were similar. ABA analogs were more effective at reducing moisture use by tomato seedlings than regular ABA and also had fewer negative effects on plant appearance. Before ABA analogs can be recommended for commercial-scale use, their impact on long-term performance needs to be determined, along with an evaluation of their cost and safety relative to other plant growth retardants.

Performance of interior spruce seedlings treated with abscisic acid analogs

This research examined the performance of interior spruce (Piceaglauca (Moench) Voss × Piceaengelmannii Parry ex Engelm.) seedlings, each group treated with one of nine abscisic acid (ABA) analogs, during the initial stages of seedling establishment under a range of environmental conditions. Interior spruce seedlings were removed from frozen storage, ABA analog treatments were immediately applied, and seedlings were tested under low root temperature or moderate drought cycle conditions. Alternatively, seedlings were removed from frozen storage and held until bud break had occurred before ABA analog treatments were applied. These seedlings were then tested under severe drought or optimum environmental conditions. ABA analog 1, followed by ABA analog 2, had the most consistent performance of the nine tested ABA analogs under all combinations of environmental test conditions. These ABA analogs reduced needle conductance for 7–9 days when seedlings were tested under low root temperature conditions with only a reduction in net photosynthesis on the first day of testing. During three successive moderate drought cycles, seedlings treated with ABA analogs 1 and 2 had partial stomatal closure, thereby increasing mean shoot water potential by around 50%. During a severe drought, ABA analog 1 caused partial stomatal closure, which allowed seedlings to maintain a mean shoot water potential of greater than −3.0 MPa and a positive net photosynthesis up to 8 days longer than control seedlings. Under optimum environmental conditions, ABA analogs 1 and 2 reduced needle conductance for up to 7 days, with net photosynthesis reduced for 1 day. Root growth was not adversely affected in seedlings treated with any of the ABA analogs prior to bud break. However, when seedlings were treated after bud break, all ABA analogs reduced growth of long roots (>4.0 cm) by approximately 60%. ABA analogs 1 and 2 delayed bud break by 4 days, when compared with control seedlings. Results are discussed in reference to the establishment process of spruce seedlings on reforestation sites.