Embrapa lettuces develop at temperatures of 30°C for 45 days

Embrapa's curly lettuce cultivars, BRS Leila and BRS Mediterrânea, achieved the best performance in experiments with higher temperatures. The researchers simulated a scenario of a 5ºC increase in temperature, going from an average of 25ºC to 30ºC, for 45 days. Unlike nine other cultivars tested in the same experiment, the two developed well in the new conditions.

The study evaluated the effect of temperature on the development of lettuce plants, with the aim of anticipating the effects of changes in the planet's climate. “To this end, we worked on two air temperature values, according to the historical average observed and projected in an extreme scenario of global climate change (GCMs) for Brazil: 25ºC/20ºC and 30ºC/25ºC (day and night, respectively)”, details the researcher from Embrapa Hortaliças (DF), Carlos Pacheco.

The experiments were conducted in the research center's Plant Growth Chamber, capable of simulating atmospheric parameters such as temperature, relative humidity and carbon dioxide concentration, for example. The researcher remembers that leafy vegetables are more susceptible to heat and, among them, lettuce is the most consumed in the country according to the Brazilian Seed and Seedling Trade Association (Abcsem), which makes the work important for the effort adaptation to climate change.

Features that made the difference

The two Embrapa cultivars have characteristics capable of overcoming the increase in temperature, according to researcher Fábio Suinaga, developer of both materials. “BRS Leila presents a delay in the flowering of the plant, which makes it resist, on average, ten days more heat compared to the other lettuces tested”, reports the scientist.

BRS Mediterrânea reaches the fastest harvest point, seven days before similar cultivars on the market. “With a shorter production cycle, it is less exposed to heat and prevents early flowering”, details Suinaga. He explains that this premature flowering causes harmful effects such as stem lengthening, reduction in the number of leaves and production of latex, a substance that gives the hardwood a bitter taste. All of this reduces the commercial value of lettuce.

The commercial cultivars, under the same temperature changes, presented a series of disorders, such as bolting, edge burning, chlorosis, necrosis, plant death, in short they could not be commercialized. “When it is observed that our cultivars remained firm despite the 30º C it is a demonstration that we have genetic material adapted to certain adverse conditions”, celebrates the researcher.

The Plant Growth Chamber

The main tool for evaluating cultivars by researchers, to assess heat tolerance, has been equipment that works like a simulator.

The Plant Growth Chamber is a closed environment capable of simulating future climate scenarios. In a reduced space, it is possible to test the behavior of plants, grown in pots, based on the projection of different factors such as temperature, humidity, CO2, radiation and others. “In this simulated environment, plants are exposed to extreme conditions to identify those that are most resilient to high temperatures and other factors such as water deficit, for example,” he adds.

Next step: water stress testing

Pacheco informs that the work is part of a series of strategies to combat climate conditions. The team intends to continue studies on other fronts, in order to select materials that are increasingly tolerant to heat. “Right now we are working on heat tolerance, and in the second stage we must focus on water stress (due to excess or lack of water), involving tolerance to salinization, followed by behavior in relation to the use of bio-inputs”, announces Pacheco.