M Sc

The study entitled “Management of elevated CO 2 induced high temperature
through nutrient and biofertilizer application in tomato (Solanum lycopersicum L.)” was
undertaken with the objective of improving flowering and fruit set of tomato under elevated
CO 2 condition through nutrient and biofertilizer application. The experiment was
conducted using the Open Top Chamber (OTC) facility at the Department of Plant
Physiology, College of Agriculture, Vellyani during 2020-2021.
In the experiment, flowering and fruiting in tomato under elevated CO 2 environment,
as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out
in CRD with nine treatments and three replications. The treatments comprised of T 1 :50
ppm B + 50 ppm Zn + water spray, T 2 :75 ppm B + 75 ppm Zn, T 3 : POP 150%
N:125%P:125% K, T 4 : Azolla (soil application), T 5 :Azolla biofertilizer extract (20%)
(foliar application), T 6 : Azolla biofertilizer extract(20%)(seed treatment), T 7 :POP, KAU+
PGPR1, T 8 : Control (water spray) and T 9 : Absolute control.
Experimental results revealed that plant height, number of branches, number of
leaves and specific leaf area increased significantly under elevated CO 2 condition at
75DAS. Among the treatments, foliar spray with 50ppmB+50ppm Zn+ water spray at 40,
55and 70 DAS recorded higher plant height (57.56%) at 75DAS. Nutrient application of
150%N:125%P:125%K found to improve the number of branches (91.82%), leaves
(98.56%) and specific leaf area (40.03%) at 75DAS.
Among the physiological and biochemical parameters, total chlorophyll content,
total carbohydrate, photosynthetic rate, water use efficiency, chlorophyll fluorescence,
chlorophyll stability index and proline content recorded higher values inside OTC
compared to open condition. However, a significant reduction was noted in transpiration
rate and total soluble protein content inside OTC compared to open condition.
The foliar spray of 50ppm B+50ppm Zn+ water spray recorded high values for
chlorophyll content (1.58 mg g -1 ) and cell membrane stability index (53.83%) compared to
open condition at 75DAS. The application of POP 150% N:125% P:125% K recorded
significantly higher photosynthetic rate (21.03μmol CO 2 m -2 sec -1 ), total carbohydrate(50.04mgg -1 ), chlorophyll stability index(135.38%) and chlorophyll fluorescence
(0.74Fv/Fm). Also foliar application of 20% Azolla biofertilizer extract was found to
significantly improve the relative water content (96.15%) and water use efficiency(6.82
mmol CO 2 mol -1 H 2 O) in tomato plants under elevated CO 2 conditions.
Inside OTC, flowering delayed by 2 days and the total number of flower clusters
(5.96) also increased compared to control (4.12). Reduction in pollen viability (82.42%)
observed at higher CO 2 compared to control. But it was found to improve under treatment
T1 (50ppm B+ 50ppm Zn + water spray) which resulted in highest fruit setting percentage
(53.01%) as against the control (39.92%).
Fruiting was delayed by 3 days inside OTC. However, the fruit weight was found
to increase with water spray (54.46%), extra NPK(55.89%) and foliar spray of 50ppm B+
50ppm Zn+ water spray(57.51%). Foliar application of Azolla biofertilizer extract
(20%)(T5), 150% N:125% P:125% K(T3) than the recommended dose, as well as foliar
application 50ppm B + 50ppm Zn+ water spray (T1) improved the yield per plant by
55.79%, 63.08% and 65.22% respectively compared to control. All these treatments also
improved the quality parameters like lycopene, vitamin C, beta carotene and minerals (P,
Fe) in tomato fruits under elevated CO 2 condition.
The present study indicated the improved performance of tomato variety Vellayani
vijay upon exposure to elevated CO 2 . But flowering, fruit set and ultimately the total yield
were negatively influenced by elevated CO 2 induced high temperature. The impact of
application of extra N, P and K than the recommended doses as well as foliar application
of B and Zn indicate the changing nutrient requirement of tomato under the current scenario
of increasing atmospheric CO 2 concentration. The response of experimental plants to foliar
application of Azolla extract (20%) strongly suggest the effectiveness of this biofertilizer
in overcoming the impacts of elevated CO 2 induced high temperature and thereby
improving the plant performance. Recommendations based on the best treatments can be
developed by extending the study to field condition since the treatments were found to
improve the yield and quality even under ambient condition