MSc

The study entitled “Physiological and molecular analyses of flowering responses in amaranthus (Amaranthus spp.) and cowpea (Vigna spp.) under elevated CO2 environment” was undertaken with the objective to study the physiological, molecular and biochemical basis of elevated CO2 mediated modifications in the flowering responses of amaranthus and cowpea. The experiments were conducted at the Department of Plant Physiology, College of Agriculture, and Vellayani dudring 2015-2017. Two pot culture experiments were conducted with two varieties of amaranthus – Arun and CO-1 and two varieties of cowpea-Anaswara and Vellayani Jyothika. The technology used for CO2 enrichment was Open Top Chamber system (OTC). CO2 was released from cylinders to OTC bringing the CO2 level to 600ppm. Amaranthus and cowpea plants were raised and maintained in pots as per POP (KAU) recommentdations under elevated CO2. The control sets were kept under open field condition. Growth analysis and analyses of physiological and biochemical parameters were done at the time of harvest. The varieties which showed modification in flowering time to a greater extent under exposure to elevated CO2 were chosen for molecular analyses.
In the case of amaranthus, CO-1 variety recorded highest values of growth, physiological and biochemical parameters and was performing better when exposed to elevated CO2 condition. CO-1 recorded highest values for number of leaves (42.44), specific leaf area (219.13), root weight (1.45g), shoot weight (3.17g), total dry matter (4.93g), stomatal frequency (595.78cm -2), pigment composition (0.56mg g-1), total soluble protein (23.02mg g-1), starch (3.61mg g-1), reducing sugar (18.46mg g-1), GA (0.198 µg g-1) and nitrate reductase (0.65 µg g-1).
Flowering time was modified in CO-1 in terms of days to first flowering and days to 50% flowering (2 days); but Arun did not show any significant response in flowering time and hence CO-1 was selected for molecular analyses. Regarding quality parameters. Arun showed a reduction in ascorbic acid and vitamin A content under CO2 enrichment with an increase in oxalate content. In the case of CO-1, though ascorbic acid and vitamin A contents were less under open condition, upon exposure to higher concentrations of CO2, there was tremendous increase in these quality parameters along with oxalate content.
Both the varieties of cowpea recorded significant variations in growth, physiological and biochemical parameters when exposed to higher concentrations of CO2. But Anaswara recorded higher values for number of leaves (74.25), specific leaf area (454.53), root weight (15.04g), shoot weight (63.15g), total dry matter (78.76g), starch content (9.16mg g-1) reducing sugar (15.36mg g-1), GA (0.615 µg g-1) nitrate reductase (0.54 µ g g-1). Velllayani Jyothika recorded higher values for stomatal distribution (2893.8cm -1) and physiological and biochemical parameters like pigment composition (0.52 mg g-1)and total soluble protein (1.44 mg g-1). Flowering time was modified to a greater extent in Anaswara-2 days to first flowering and days to 50% flowering and so Anaswara was selected for molecular analyses.
CO2 enrichment was found to influence the quality parameters in amaranthus. CO-1 showed a tremendous increase in ascorbic acid and vitamin A, but there was an increase in oxalate content also. During the period of study, environmental factors like temperature, humidity and sun shine hours were measured. There was an increase of 70C an average during the period and also an increase in leaf temperature.
For gene expression studies flowering locust (FT) was selected. The DNA of Flowering locus T was amplified from Anaswara and CO-1. Differential expression was observed in both the crops under elevated CO2 condition.
In the present study, both cowpea and amaranthus were found to be responding to elevated CO2 in terms of flowering time. This can be correlated with the higher photosynthate accumulation with a net positive effect on growth parameters. The increased gibberellic acid level displayed by both the crops upon CO2 enrichment can also play a role in signaling the crosstalk between reproduction and other developmental processes. Understanding the mechanisms involved in the regulatory network modulating floral initiation in response to elevated CO2 and elevated temperature will facilitate understanding and identifying options to develop plants better adapted to changing climate.