Am thinking of trying to harvest co2 and capture it in absorption material and then extract co2 either in the nutrients or directly into the soil.
im guessing co2 will just escape the tent through ventilation without consistency so im wondering will there be much benefit to use co2 enriched soil
I think soil, may want Oxygen vs CO2. I think they saw some initial benefit, but prolonged use, was detrimental. But still needs more research.
We investigated the fate of carbon dioxide (CO2 ) absorbed by roots or internally produced by respiration using gas exchange and stable isotopic labeling. CO2 efflux from detached leaves supplied with bicarbonate/CO2 solutions was followed over six cycles. CO2 effluxes were detected when bicarbonate solution at high pH was used, corresponding to 71-85% of the expected efflux. No CO2 efflux was detected when CO2 solutions at low pH were used but CO2 efflux was subsequently detected as soon as bicarbonate solutions at high pH were supplied. By sealing the leaf and petiole in a plastic bag to reduce diffusion to the atmosphere, a small CO2 efflux signal (14-30% of the expected efflux) was detected suggesting that CO2 in the xylem stream can readily escape to the atmosphere before reaching the leaf. When the root-zones of intact plants were exposed to CO2 solutions, a significant efflux from leaf surface was observed (13% of the expected efflux). However, no signal was detected when roots were exposed to a high pH bicarbonate solution. Isotopic tracer experiments confirmed that CO2 supplied to the root-zone was transported through the plant and was readily lost to the atmosphere. However, little 13 C moved to the shoot when roots were exposed to bicarbonate solutions at pH 8, suggesting that bicarbonate does not pass into the xylem.
© 2018 Scandinavian Plant Physiology Society.
For plants to grow normally, a good rhizosphere gas environment is required. The CO2 concentration changes continuously with different soil aeration conditions, which has a great impact on the growth, development, and yield of crops. The CO2 concentration in the soil close to the plant root system often reaches values up to ten-fold that of the ambient atmosphere [
1,
2,
3]. Root and soil microorganisms produce CO2 through respiration, which accumulates in the root zone at concentrations normally between 0.2% and 0.5%, but can reach 20% under special circumstances [
4]. The actual CO2 concentration in the soil also depends on the soil water content, soil type, soil depth, microbial biomass, and the activities of soil microorganisms. Responses to high CO2 soil environment have received increased attention recently in several crop species [
5,
6,
7,
8]. However, little information is available regarding the molecular mechanisms of plants in response to elevated root-zone CO2 conditions, especially at the transcriptome level.
The effects of excessive root-zone CO2 on plant growth, nutrient absorption, and utilization vary with plant species [
9]. Nitrogen is an essential macronutrient for plant growth and basic metabolic processes. High levels of CO2 in the root-zone promoted the growth of tomato seedlings and increased their NO3− uptake, especially under salinity stress and high air temperature [
4,
10]; however, there was no significant difference in NH4+. In lettuce, high levels of root-zone CO2 could alleviate the midday depression of photosynthesis and negative impacts of high air temperature on photosynthesis [
11], and promoted NO3− uptake and the growth of lettuce plants in the greenhouse [
12,
13]. By contrast, high root-zone soil CO2 had a negative impact on morphological and physiological indicators, such as plant height, root length, chlorophyll content, photosynthesis rate, stomata conductance, and NO3− absorption and assimilation in soybean [
14], maize [
5], barley [
15], and bean [
7]. Previous studies have implied that elevated root-zone CO2 acted as a weak acid, causing acidification in root cells, and inhibition of nutrient uptake and the root respiration rate [
16]. Moreover, a high soil CO2 concentration itself might be toxic to plant growth in many plant species, and under certain conditions, CO2 toxicity is a more important factor in plant growth than O2 deficiency [
6]. Thus, elevated CO2 concentrations in the root-zone could have either positive or negative consequences for plant growth. The differences in the effects of root-zone CO2 on plants could be caused by differences in plant species, treatment time, the plant developmental period, and the CO2 concentration applied [
11,
17].
The oriental melon (
Cucumis melo var.
makuwa Makino) is one of main agricultural products that is widely cultivated in some eastern Asian countries. It is sensitive to the root-zone gas environment, and often suffers from root-zone low O2 and high CO2 stress in irrigated field cultivation. The responses of melon to root-zone hypoxia have been widely reported [
18,
19]. By contrast, there is little information on the mechanism of the oriental melon’s response to elevated root-zone CO2, especially at the transcriptome level. In addition, the molecular mechanism of the influence of root-zone CO2 on plant growth and mineral nutrient absorption has not been definitively proved.
The present study aimed to explore the molecular mechanism of root nitrogen metabolism in the oriental melon under elevated root-zone CO2. We designed an aeroponic culture system that could automatically control the root-zone CO2 concentration. Based on a transcriptome analysis in roots, we investigated the root morphology and root tip cell ultrastructure under different CO2 concentrations, including three treatments: Ambient air 0.037% (control check (CK)), elevated CO2 concentrations 0.5% (T1), and 1.0% (T2). Differentially expressed genes (DEGs) involved in nitrogen metabolism in different CO2 concentrations were screened by combining the changes of root morphology and the physiological index. Moreover, we analyzed the activities of nitrogen metabolism enzymes, and validated the sequencing accuracy of key genes using quantitative real-time PCR (qPCR). The results provided a reasonable basis to further investigate the functions of candidate genes, their transcriptional regulation, and the effective regulation of nitrogen in the oriental melon under elevated root-zone CO2.
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2. Results
2.1. Effects of Elevated Root-Zone CO2 on Root Morphology
Root morphology analysis (
Figure 1;
Table 1) showed that plants grown under elevated root-zone CO2 treatment had longer roots, a greater number of total root tips, and a larger root surface area at 3 day of treatment compared with those under ambient CO2 concentrations, although the resistance against elevated root-zone CO2 began to decline on the sixth day of treatment. The root length, the root surface area, and the number of roots with a diameter of 0.5–2.0 mm under T1 and T2 treatment were not significantly different at 6 day, compared with those of plants under CK (the red arrows indicated). On the ninth day, the root length, root surface area, and the number of major absorbing roots with diameter of 0–0.5 mm were remarkably lower under T1 and T2 treatments than in the CK group (the red arrows indicated). The main root length was reduced by 8.43% and 20.90%, respectively, and root surface area decreased by 20.35% and 52.05%, respectively, compared with the CK group. The data indicated that root growth was enhanced during short-term high CO2 exposure; however, with prolonged treatment, inhibitory effects were more significant.
