Growth and photosynthetic efficiency promotion of sugar beet (Beta vulgaris L.) by endophytic bacteria

Abstract

Very little is known about the physiological interactions between plants and endophytic bacteria. We investigated the impact of three endophytic bacteria, Bacillus pumilus 2-1, Chryseobacterium indologene 2-2, and Acinetobacter johnsonii 3-1, on the photosynthetic capacity and growth of sugar beet. Endophyte-free plants were obtained first and infected with the bacteria. Measurements of total chlorophyll content revealed very significant differences between endophyte-free beet plants and some infected by endophytic bacteria. The maximum photochemical yield (Fv/Fm) was used to determine any photosynthetic effect on plants caused by biotic or abiotic factors. After 30 days of growth, there was significantly higher Fv/Fm for endophyte-infected than endophyte-free plants. The light response curves of beet showed that photosynthetic capacity was significantly increased in endophyte-infected plants. Photosynthesis of endophyte-free plants was saturated at 1,300 micromol m(-2) s(-1), whereas endophyte-infected plants were not saturated at the irradiance used. The effect seemed to be due to promotion of electron transport in the thylakoid membranes. Promotion of photosynthetic capacity in sugar beet was due to increased chlorophyll content, leading to a consequent increased carbohydrate synthesis. It is possible that the increased maximum yield of photosynthesis in sugar beet was promoted by phytohormones and produced by the bacteria.

Endophytic bacteria affect sugarcane physiology without changing plant growth

“…As such reduction did not result in low soluble sugars content (Figure 2b), our data indicate the presence of other sugars derived from sucrose hydrolysis. In fact, Shi et al (2010) found higher fructose concentration in leaves of plants treated with endophytic bacteria. The inocula did not change Sta and NSC concentrations, regardless sugarcane genotype (Figures 2c, d).…”

“…These changes suggest an improved absorption of light energy and use in photochemistry, a key physiological process responsible for ATP and NADPH production in chloroplasts. Shi et al (2010) also reported that bacteria inoculation caused an increase in ETR and improved photosynthesis, suggesting the presence of unknown compounds produced by bacteria that could increase ETR and chlorophyll metabolism. The presence of bacteria in leaves may also upregulate photosynthetic genes related to ferredoxin and NADPH ferredoxin (Bilgin et al 2010).…”

“…/1678 quantum efficiency of photosystem II, electron transport in the thylakoid membranes, leaf CO 2 assimilation and carbohydrate content than untreated ones (Shi et al 2010). In general, growth promotion is usually attributed to improved plant nutrient acquisition (Barretti et al 2008) and production of phytohormones as indoleacetic acid by bacteria (Shi et al 2010). Biological nitrogen fixation is another advantage of the association between diazothrophic bacteria and plants and it has been shown that sugarcane varieties can get at least 40 kg N•ha -1 yr -1 through this process (Urquiaga et al 2012).…”

“…Sugar beet plants treated with endophytic bacteria showed higher potential DOI: http://dx.doi.org/10.1590DOI: http://dx.doi.org/10. /1678 quantum efficiency of photosystem II, electron transport in the thylakoid membranes, leaf CO 2 assimilation and carbohydrate content than untreated ones (Shi et al 2010). In general, growth promotion is usually attributed to improved plant nutrient acquisition (Barretti et al 2008) and production of phytohormones as indoleacetic acid by bacteria (Shi et al 2010).…”

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“…Shi et al [15] investigated the impact of three endophytic bacteria species, Bacillus pumilus, Chryseobacterium indologene, and Acinetobacter johnsonii, on the photosynthetic capacity of sugar beet (Betula vulgaris). The measurements of total chlorophyll content revealed very significant differences between non-inoculated beet plants and those inoculated with endophytic bacteria.…”