For the first time, an enthusiasm for gambling has been identified in plants. The discovery is not entirely surprising, since a facility for assessing odds has been revealed in single-celled slime molds, but nevertheless sheds light on how sophisticated plants can be in their responses to their environment, and opens up exciting research possibilities.

Plants lack animals' luxury of moving to more promising locations when nutrients are scarce. However, if soil is richer in one direction than the other they will adjust the concentration of their roots. just as they will grow towards, and even follow, the light in shady locations.

Efrat Dener, a master's student at Ben Gurion University, Israel, tested this capacity by growing pea plants so that their roots were split between two pots. The choice of Pisum sativum harks back to its role in Mendel's discovery of the laws of genetics.

When one pot was consistently supplied with more nutrients extra roots grew in that direction, but Dener also sought something more complex. She made the same amount of nutrients available, on average, in both pots, but kept one consistent while the other varied with time.

^{Schematic of the experiment, and the nutrients supplied per day in the variable pot. Dener et al/Current Biology}

In Current Biology, Dener reported that the peas' preference varied depending on average nutrient concentrations. When each pot was rich in nutrients, the plants preferred the peace that comes with stability, but when each, on average, offered a poor diet the plants prioritized the variable pot.

Equivalent studies of both humans and animals have produced similar findings, although the paper argues the pattern is clearer here.

The reaction makes sense. If the stable pot gives a plant as much as it needs, why be greedy and chase bigger winnings with the unreliable alternative? But if the consistent pot offers such a poor return the plant cannot flourish, it is rational to gamble on something that might possibly reward you.

We see the same behavior outside the lab. It is common for the poor to gamble more than the comfortably off, certainly as a percentage of income, and sometimes in absolute terms. They may know the game is rigged, but it offers a rare opportunity to hope. 

“We do not conclude that plants are intelligent in the sense used for humans or other animals, but rather that complex and interesting behaviors can theoretically be predicted as biological adaptations – and executed by organisms – on the basis of processes evolved to exploit natural opportunities efficiently,” said co-author Alex Kacelnik of the University of Oxford in a statement.

Kacelnik added: “We do not yet know how the plants' sense variance functions, or even if their physiology is specifically adapted to respond to risk, but the findings lead us to look even at pea plants as dynamic strategists and to model their decision processes just as one would model an intelligent agent.”

The authors are excited by the potential of further work to explore natural selection and economic decision making in controlled environments free from irrational emotions.

^{When going gambling, you might want to take a friendly pot plant. Dice players (the gamblers) by follower of Mathieu Le Nain/ Shutterstock.}