MSc

The study entitled “Impact of bio-fertilizers on root character and
reproductive physiology of rice (Oryza sativa L.)” was undertaken with the objective
of elucidating the effect of bio-fertilizers on hormonal status, root character and
reproductive traits like flowering, pollen characteristics, spikelet fertility and yield in
rice. The experiment was conducted as a pot culture experiment at the Department of
Plant Physiology, College of Agriculture, Vellayani during 2020-2021. The
experiment was laid out in CRD with ten treatments and three replications. The
treatments comprised of T1: POP, KAU + Azolla, T2: POP, KAU + AMF, T3: POP,
KAU + PGPR Mix I, T4: POP, KAU + PSB, T5: POP, KAU + KSB, T6: T1 + AMF,
T7: T1 + PGPR Mix I, T8: T1 + PSB, T9: T1 + KSB and T10: Control.
The experimental results revealed that plant height, number of tillers per
plant, dry matter production, number of productive tillers, specific leaf area, number
of grains per panicle, 1000 grain weight, grain yield, straw yield and harvest index
increased by the application of different bio-fertilizers. Among the treatments,
incorporation of Azolla and PGPR Mix I along with POP, KAU recommendations
(T7) recorded highest values in the cases of plant height (99.83 cm), number of tillers
(15.33), straw yield (42.24 g per plant) and dry matter production (84.69 g per plant)
compared to control. But the number of productive tillers (12.66), specific leaf area
(372.98 cm2
g
-1
), number of grains per panicle (129), 1000 grain weight (24.16 g),
grain yield (31.85 g per plant) (36.02%) and harvest index (0.46) were found to be
maximum in T6 (POP, KAU + Azolla + AMF) compared to the control.
Incorporation of Azolla and AMF along with POP recommendations (T6)
significantly reduced the number of days to heading (6 days) as well as number of
days to 50% flowering compared to control.
A significant increase in physiological and biochemical parameters such as
total chlorophyll content, total carbohydrate, protein content and reducing sugar was
achieved by the application of different bio-fertilizers. Among the treatments, T6
(POP, KAU + Azolla + AMF) showed significant increase in total chlorophyll
content (71.05%), total carbohydrate (73.87%), protein content (35.10%) and
reducing sugar (19%) compared to control at booting stage.
Hormonal status (IAA and GA contents) and root characters such as root
length, root diameter, stele diameter, width of aerenchyma, late metaxylem number,
late metaxylem diameter and early metaxylem number were found to significantly
improve by the application of different bio-fertilizers. Among the treatments, IAA
and GA in leaf tissue at 60 DAS (2.28 and 1.09 µg g-1
) and 80 DAS (2.39 and 1.15
µg g-1
) were found to significantly increase in T7 (POP, KAU + Azolla + PGPR Mix
I) compared to control. However, T6 (POP, KAU + Azolla + AMF) showed
significant improvement in root characters such as root length (31.72 cm), root
diameter (1.03 mm), stele diameter (0.45 mm), width of aerenchyma (67.01 mm),
late metaxylem number (5.01), late metaxylem diameter (0.052) and early
metaxylem number (28.94) compared to the control.
Bio-fertilizer application was found to enhance the grain quality significantly
by enhancing the levels of total carbohydrate, protein, phosphorus, calcium, iron and
zinc and by reducing amylose content. Among the treatments, T6 (POP, KAU +
Azolla + AMF) showed significant reduction in amylose content (16%) in grains
compared to control. Incorporation of Azolla and AMF along with POP
recommendations (T6) showed significant increase in protein content (55.08%) and
nutrient status such as phosphorus (58.33%), calcium (61.76%), iron (72.67%) and
zinc (66.89%) in grains compared to control whereas carbohydrate content (24.02%)
and iron content (74.32%) in grains were found to significantly increase in T7 (POP,
KAU + Azolla + PGPR Mix I).
In the present investigation, incorporation of Azolla and PGPR along with
POP (KAU) recommendations were found to improve hormonal status and dry
matter production whereas, incorporation of Azolla and AMF along with POP
recommendations were found to improve physio-morphological and biochemical
parameters as well as yield and quality parameters in the rice variety Uma. These
biofertilizers were also effective in improving the root characteristics in terms of
metaxylem number and diameter which will have an impact on water and mineral
uptake and translocation. It will also help to improve water-use efficiency and impart
stress tolerance through better exploitation of soil water and nutrient reserves.
The benefits of biofertilizers can be exploited in soils low in available
nutrients. Under drought conditions their association can augment water uptake and
transport to the host enhancing stress tolerance. This role of biofertilizers can
potentially strengthen plant adaptability to changing environment. Standardization
of a recommendation can be undertaken for improving the field performance and
quality of rice based on the best results of the current programme.