Assessing the Impact of Higher Levels of CO2 and Temperature and Their Interactions on Tomato (Solanumlycopersicum L.)

Adaptive responses to elevated CO2 in fruit species with different phloem loading mechanisms

Introduction

It has been suggested that the mechanism of phloem loading, that is apoplastic or symplastic loading, may affect a plant's ability to adapt to elevated CO2 levels. Strawberry (Fragaria × ananassa) and tomato (Solanum lycopersicum) are two fruit crops that use different mechanisms to load sugars into the phloem - the former symplastically and the latter apoplastically - yet both species can increase their yields when grown in a CO2-enriched environment. In this study, we subjected strawberry and tomato plants to long-term CO2 enrichment to determine the morphological and physiological adaptations that enable them to increase their yields in response to higher CO2 levels.

Methods

Transplanted tomato and strawberry plants were subjected to ambient (400 ppm) and elevated (800 ppm) CO2 for three months. We examined various parameters associated with growth, yield, photosynthesis, and carbon allocation by means of phenotyping, gas exchange analysis, and 13C labelling combined with isotope ratio mass spectrometry.

Results

We found that CO2 enrichment promoted growth and reproductive development in both species, resulting in more flowers per plant (tomato and strawberry), larger crown (strawberry), and, eventually, higher yields. Gas exchange analysis and A/c i curves revealed that elevated CO2 increased carbon assimilation rate in strawberry, but not in tomato - the latter being limited by Rubisco's carboxylation efficiency. Finally, whereas both species prioritized fruit development over the development of other sink organs, they were both limited by carbon export at elevated CO2, since new photoassimilates were equally distributed to various sinks between CO2 treatments.

Discussion

The findings suggest that both species will benefit from future increases in CO2 levels and support current glasshouse practices entailing CO2 enrichment. Those benefits probably stem from an enhanced performance of both species at early developmental stages, as differences in carbon assimilation rate (tomato) and carbon allocation between treatments at late developmental stages were absent. Moreover, crop adaptation to elevated CO2 seems to depend on the ability of each species to respond to elevated CO2, rather than on the phloem loading mechanism per se.

Revisiting Changes in Growth, Physiology and Stress Responses of Plants under the Effect of Enhanced CO2 and Temperature

Climate change has universally affected the whole ecosystem in a unified manner and is known to have improbable effects on agricultural productivity and food security. Carbon dioxide (CO2) and temperature are the major environmental factors that have been shown to increase sharply during the last century and are directly responsible for affecting plant growth and development. A number of previous investigations have deliberated the positive effects of elevated CO2 on plant growth and development of various C3 crops, while detrimental effects of enhanced temperature on different crop plants like rice, wheat, maize and legumes are generally observed. A combined effect of elevated CO2 and temperature has yet to be studied in great detail; therefore, this review attempts to delineate the interactive effects of enhanced CO2 and temperature on plant growth, development, physiological and molecular responses. Elevated CO2 maintains leaf photosynthesis rate, respiration, transpiration and stomatal conductance in the presence of elevated temperature and sustains plant growth and productivity in the presence of both these environmental factors. Concomitantly, their interaction also affects the nutritional quality of seeds and leads to alterations in the composition of secondary metabolites. Elevated CO2 and temperature modulate phytohormone concentration in plants, and due to this fact, both environmental factors have substantial effects on abiotic and biotic stresses. Elevated CO2 and temperature have been shown to have mitigating effects on plants in the presence of other abiotic stress agents like drought and salinity, while no such pattern has been observed in the presence of biotic stress agents. This review focuses on the interactive effects of enhanced CO2 and temperature on different plants and is the first of its kind to deliver their combined responses in such detail.

Feeding the world: impacts of elevated [CO2] on nutrient content of greenhouse grown fruit crops and options for future yield gains

Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO2] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80% are observed when plants are cultivated at 1000 ppm [CO2], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO2] for improving yield and quality in greenhouse crops. The major focus of this review is to bring together 50 years of observations evaluating the impact of elevated [CO2] on fruit yield and fruit nutritional quality. In the final section, we consider the need to engineer improvements to photosynthesis and nitrogen assimilation to allow plants to take greater advantage of elevated CO2 growth conditions.

Climate Stressors on Growth, Yield, and Functional Biochemistry of two Brassica Species, Kale and Mustard

Due to climate change, the attainment of global food security is facing serious challenges in meeting the growing food demand. Abiotic stresses are the foremost limiting factors for agricultural productivity. However, not much information is available on the effect of multiple abiotic stresses on the morphological and biochemical aspects of kale and mustard. Therefore, an experiment was designed to study the effects of UV-B radiation, CO₂ concentration, and high temperature on the growth, yield, and biochemistry of two Brassica species, namely B. oleracea L. var. acephala Winterbor F1 (hybrid kale) and B. juncea var. Green wave O.G. (mustard greens), which were grown under optimal nutrients and soil moisture conditions in soil-plant-atmosphere-research (SPAR) units. Two levels of UV-B radiation (0 and 10 kJ m^-2 d^-1), two concentrations of CO₂ (420 and 720 ppm), and two different temperature treatments (25/17 °C and 35/27 °C) were imposed 12 days after sowing (DAS). Several morphological and biochemical parameters were measured at harvest (40 DAS) in both species. All the traits declined considerably under individual and multi-stress conditions in both species except under elevated CO₂ levels, which had a positive impact. Marketable fresh weight decreased by 64% and 58% in kale and mustard plants, respectively, growing under UV-B treatment. A slight increase in the chlorophyll content was observed in both species under the UV-B treatment alone and in combination with high temperature and elevated CO₂. Understanding the impacts of high temperature, CO₂, and UV-B radiation treatments on leafy vegetables, such as kale and mustard, can help to improve existing varieties to enhance resilience towards environmental stresses while simultaneously improving yield, morphology, and biochemistry in plants.

Effect of Elevated Carbon Dioxide Exposure on Nutrition-Health Properties of Micro-Tom Tomatoes

(1) Background: The anthropogenically induced rise in atmospheric carbon dioxide (CO₂) and associated climate change are considered a potential threat to human nutrition. Indeed, an elevated CO₂ concentration was associated with significant alterations in macronutrient and micronutrient content in various dietary crops. (2) Method: In order to explore the impact of elevated CO₂ on the nutritional-health properties of tomato, we used the dwarf tomato variety Micro-Tom plant model. Micro-Toms were grown in culture chambers under 400 ppm (ambient) or 900 ppm (elevated) carbon dioxide. Macronutrients, carotenoids, and mineral contents were analyzed. Biological anti-oxidant and anti-inflammatory bioactivities were assessed in vitro on activated macrophages. (3) Results: Micro-Tom exposure to 900 ppm carbon dioxide was associated with an increased carbohydrate content whereas protein, minerals, and total carotenoids content were decreased. These modifications of composition were associated with an altered bioactivity profile. Indeed, antioxidant anti-inflammatory potential were altered by 900 ppm CO₂ exposure. (4) Conclusions: Taken together, our results suggest that (i) the Micro-Tom is a laboratory model of interest to study elevated CO₂ effects on crops and (ii) exposure to 900 ppm CO₂ led to the decrease of nutritional potential and an increase of health beneficial properties of tomatoes for human health.