Climate Change Effects on Plant Development: Comprehensive Insights

• Climate change can alter plants’ roots, vegetation, and reproductive development.
• Climate change effects on plant development can sometimes be similar across species or depend on tissue, species, genotype, and development stage.
• Plants are most sensitive to temperature and drought stress effects during the reproductive phase.

Several features characterize climate change, like higher concentrations of greenhouse gases, higher temperatures, changes in precipitation, extreme weather, and drought. The environmental stressors will alter plants’ molecular, cellular, morphological, and physiological responses. Taken together, the impact on plant development can be significant.

Based on Gray & Brady’s 2016 publication, this article summarizes major changes in the development of vegetative growth, root systems, and reproductive phases due to higher carbon dioxide levels, higher temperatures, and more droughts.

Vegetative Development

The shoot system with leaves, which has the most extensive surface interface with the environment, experiences contradictory impacts from the three climate features.

Elevated CO2 Effects

Higher concentrations of carbon dioxide (CO2) have effects specific to species, cells, tissues, space, and time.

Leaf growth: More CO2 acts as a fertilizer to improve leaf growth. The fertilizer effect varies and is higher in C3 than in C4 plants. Leaf size gets larger due to more cell production and expansion. Higher CO2 makes younger leaves larger than mature leaves, but palisade mesophyll cells increase in size in young and old leaves. The ratio of stomata to epidermal cells reduces due to higher CO2 levels.

Shoot system: Shoot architecture changes as the number of vegetative nodes and branches increases; for example, in soybeans, see Figure 1. Crops like wheat and rice will grow more tillers due to elevated CO2.

Rising Temperature Impacts

The rate of leaf initiation, expansion, and duration of leaf expansion increase as temperature rises from 6–26°C. The number of leaves added throughout the vegetative phase will also increase till a maximum threshold between 26 to 37°C that is species-specific; for example, the maximum optimum temperature is 26°C for wheat and 37°C for cotton. Due to temperature stress, leaves, stem development, and morphological responses are similar to shade avoidance and involve petiole and hypocotyl elongation. The molecular mechanisms underlying these responses are unknown. Beyond the maximum threshold, heat can become stress, leading to wilting and permanent damage to leaves and shoots.

Drought Stress Effects

Contrary to higher CO2 and temperature, drought reduces leaf expansion in several species. Cell division and expansion critical for leaf expansion are slow or absent; sometimes, the standard leaf final size is never attained. The overall size of the plant is also reduced by drought.

Figure 1: Effect of elevated CO2 on plant development, Gray and Brady (2016). (Image credits: https://www.sciencedirect.com/science/article/pii/S0012160616302640)

Root System

Changes to roots due to drought are the most well-known climate change response, but there is enough information to show that higher CO2 and temperatures can also cause significant impact. Climate change effects on plant development include alterations in root biomass, root length, and root architecture, which are critical for water and nutrient acquisition.

Elevated CO2 Effects

Root biomass surges in several crops and forest trees have been observed, leading to a higher root-shoot ratio. This suggests that plants invest in getting more water and nutrients during elevated CO2 levels to support increased plant growth.

Minirhizotron studies show an increase in several root parameters:

• Root length in shallow and intermediate soil depths.
• More CO2 and drought increase the number and density of root nodules.
• More branching and lateral roots alter architecture to aid in the search for water.
• Increased root diameter, especially in stele and cortex tissues.

Higher root density, branching, and reduced root elongation are seen across species.

Soil Temperature Rise Effects

Soil temperature is closely correlated to air temperature, so the projected air warming between 1.0–3.7°C will affect underground systems too. Effects can be direct or indirect due to changes in plant carbon allocation to the roots, which alter functions like water and nutrient uptake or root respiration.

As in the case of vegetative parts, rising temperatures increase root growth till a species-specific maximum threshold. Roots elongate and branch at higher angles due to higher temperatures. The effect is more in lateral roots sensitive to temperatures than tap roots. So, at shallow depths, root distribution and density increase. For example, more and longer lateral roots grow in sunflower and cotton up to 30°C and 35°C, respectively. Beyond these temperatures, root growth begins to decline.

Soil temperature projections are complex as they depend on soil texture, moisture, and insulation due to vegetation cover or snow.

Drought Stress Effects

In contrast to vegetative growth, drought maintains or even enhances root growth. The growth rate will slow, but the reductions are less than those seen in shoot growth, as seen in maize, squash, soybeans, or cotton.

Many species grow deeper roots during drought. The tap root elongates during drought, and plants develop more lateral roots to alter root architecture and distribution for better water acquisition.

Reproductive Parts

The reproductive phase covers flowering, gamete formation, pollination, fertilization, seed development, and grain-filling. Temperature stress effects on this phase can be more significant than during vegetative growth.

Elevated CO2 Effects

Elevated CO2 boosts seed yield in several crops, but the nutritional value is lower due to less nitrogen, protein, iron, and zinc content.

A meta-analysis of 79 species showed that elevated CO2 consistently increases reproduction- by boosting the number of flowers, fruits, and seeds by 16-19% and total seed mass by 25%. Cultivated crop species experienced an average of 28% higher fruit production, while wild species showed only a 4% increase in fruits. Responses in cultivated showed less variability than wild species.

Higher CO2 can extend the vegetative phase, allowing plants to accumulate more biomass to increase seed yield. However, an extension in the vegetative phase due to higher CO2 can delay the onset of the reproductive phase or cause complete reproductive failure, but the effect is genotype-specific. Some species and varieties can also accelerate or have no effects due to elevated CO2. For soybeans, it has delayed reproduction due to a longer growing phase, but the flowering and seed stages also last longer.

Figure 2: Effect of climate change-related increased temperature and drought stress on reproductive systems, Gray and Brady (2016). (Image credits: https://www.sciencedirect.com/science/article/pii/S0012160616302640)

Elevated Temperature Effects

The impact on yield will vary on geography. For example, soybean yield is expected to increase by 1.7% in the cooler Midwestern USA but decrease by 4% in the southern and warmer states. The maximum threshold before adverse effects set in can differ for vegetative and reproductive phases. For example, rice vegetative growth peaks at 33°C, but temperatures above 25°C reduce grain formation and yield.

As temperature rises to a maximum threshold, reproductive development occurs earlier in many crops, as vegetative phase development is completed faster. Temperatures beyond the threshold will slow or completely stop reproductive development. Early reproduction leaves less time for biomass accumulation for proper gamete formation. However, these effects are species-specific.

The influence of heat on reproduction is due to the extreme sensitivity of male gametophytes to higher temperatures; pollen viability reduces significantly due to heat. Female gametophytes or pistils are less heat-resistant but can contribute to reproductive failure if ovules are aborted. Even if fertilization occurs, the quality and number of seeds is poor.

A heat wave during early seed development will have more effect (10–17%) than in later stages.

Changes in winter chilling temperatures can affect fruit and nut species flowering and fruit set.

Drought Stress Effects

Flowering time can be crucial for reproductive success during drought. Plants may try drought escape mechanisms from a late-season water deficit by flowering and completing reproduction early. Drought avoidance mechanisms like increased water efficiency are used during early-season drought.

Plants are most susceptible to drought during the reproductive phase, as male floral parts and gametophyte development are affected. Water deficit during inflorescence can slow or inhibit development partially or entirely. Plants protect female reproductive parts during drought as pollen is tiny and numerous.

Interactive Effects

The climate change effects on plant development described above are the results of research that studies the impact of only one factor on the plants’ development. However, in natural conditions, several environmental changes co-occur. Since the effects of the three factors are sometimes contradictory, it is difficult to draw inferences on plant responses to climate change. For example, a few interactive studies show that C02 fertilization effects on leaf expansion are reduced when drought also occurs. Similarly, yield increase due to CO2 will also be affected by higher temperatures; for example, hot regions of India will see a 14% decrease in wheat yield.

Studying Climate Change Effects on Plant Development

Given the complexity and the species and tissue-specific nature of climate change effects, research on plant development is likely to continue. Some of the non-destructive precision tools produced by CID Bio-Science Inc. that scientists can use for plant development studies are as follows:

• Leaf studies could use the CI-202 Portable Laser Leaf Area Meter and CI-203 Handheld Laser Leaf Area Meter.
• Canopy studies need a CI-110 Plant Canopy Imager.
• Root studies will benefit from minirhizotron systems using CI-600 In-Situ Root Imager and CI-602 Narrow Gauge Root Imager.

Scientists trust these tools, which have also been mentioned in several peer-reviewed publications.

Sources

Gray, S. B., & Brady, S. M. (2016). Plant developmental responses to climate change. Developmental biology, 419(1), 64-77.

Singh, B.K., Delgado-Baquerizo, M., Egidi, E. et al. Climate change impacts on plant pathogens, food security and paths forward. Nat Rev Microbiol 21, 640–656 (2023). https://doi.org/10.1038/s41579-023-00900-7

Gray, E. (2021, Sept 28). NASA at Your Table: Climate Change and Its Environmental Impacts on Crop Growth. Retrieved from https://climate.nasa.gov/news/3116/nasa-at-your-table-climate-change-and-its-environmental-impacts-on-crop-growth/