Effects of Short-term Hypergravity Exposure on Germination, Growth and Photosynthesis of Triticum aestivum L.

Abstract

Numerous studies have been carried out to investigate the hypergravity effect on plants, where seedlings (4-5 days old) were continuously exposed and grown under hypergravity condition. Here, we have used a novel 'shortterm hypergravity exposure experimental method' where imbibed caryopses (instead of seedlings) were exposed to higher g values ranging from 500 g to 2500 g for a short interval time of 10 minutes and post short-term hypergravity treated caryopses were grown under 1 g conditions for five days. Changing patterns in caryopsis germination and growth, along with various photosynthetic and biochemical parameters were studied. Results revealed the significant inhibition of caryopsis germination and growth in shortterm hypergravity treated seeds over control. Photosynthesis parameters such as chlorophyll content, rate of photosynthesis (P N ), transpiration rate (Evap) and stomatal conductance (Gs), along with intracellular CO 2 concentration (C int ) were found to be affected significantly in 5 days old seedlings exposed to short-term hypergravity treatment. In order to investigate the cause of observed inhibition, we examined the α-amylase activity and antioxidative enzyme activities. α-amylase activity was found to be inhibited, along with the reduction of sugars necessary for germination and earlier growth in short-term hypergravity treated caryopses. The activities of antioxidant enzymes such as catalase and guaiacol peroxidase were increased in short-term hypergravity treated caryopses, suggesting that caryopses might have experienced oxidative stress upon short-term hypergravity exposure.

Effects of High g Values on Growth and Chlorophyll Content in Hydrated and Dehydrated Wheat Seeds

“…Decrease in chlorophyll content was observed in hypergravity samples. This is in consistent with the results obtained for rice [11] and wheat [14,15]. However, no change in seed germination percentage, growth and chlorophyll content was observed for seeds exposed to hypergravity without water or any medium inside the test tubes at the time of exposure.…”

A hypergravity environment increases chloroplast size, photosynthesis, and plant growth in the moss Physcomitrella patens

“…Other physiological alterations in the leaves of bryophytes related to the photosynthesis rate may be possible with hypergravity. Exposure to short-term strong hypergravity (500-2000× g ) under dark conditions was previously reported to induce reductions in the chlorophyll content and photosynthesis rate in wheat seedlings grown for five days under 1× g (Vidyasagar et al 2014 ), which suggests that some alterations in chloroplast functions and impairments in photosynthetic biochemistry are caused by hypergravity.…”

Short-Term Hypergravity-Induced Changes in Growth, Photo synthetic Parameters, and Assessment of Threshold Values in Wheat (Triticum aestivum L.)

“…The decrease in stomatal conductance may also cause a decline inthe transpiration rate (Farquhar and Sharkey, 1982;Jeanguenin et al, 2017). In addition to the above argument, contributions from other factors such as reductions in chlorophyll content (Vidyasagar et al, 2014) and changes in chloroplast size (Takemura et al, 2017) might also be responsible for the reduced rate of photosynthesis in the present study. Chlorophyll fluorescence gives the information about change in the efficiency of photochemistry of photosystem II (Maxwell and Johnson, 2000).…”

“…In addition, the information on hypergravity-induced changes in chlorophyll fluorescence parameters characterized by the Kautsky fluorescence induction curve (photochemical activity of PS II) is limited. Only few reports have documented the effects of hypergravity on photosynthetic and chlorophyll fluorescence parameters; however, these studies were not aimed at threshold values (Vidyasagar et al, 2014;Takemura et al, 2017). This could be due to the negative impact of hypergravity on plant growth and development, which might have discouraged researchers from extending hypergravity studies for understanding photosynthesis.…”

“…Recent advances in space and gravitational biology have shown that an alteration in the gravity value above or below Earth's gravity (1 g) produces measurable changes in biological systems. Indeed, it is well documented that microgravity has positive effects while hypergravity has negative effects on plant growth and development (Waldron and Brett, 1990;Hoson et al, 1996;Jagtap et al, 2011;Vidyasagar et al,2014). Although several studies have been conducted on ground-based low gravity (simulated microgravity), the use of plant systems for studies under a higher range of hypergravity conditions is limited, which may be due to the negative impact of high g forces on plants.…”