This study investigated the effects of temperature on seed production in rice. Seed priming with ascorbic acid or salicylic acid improved seed germination and performance at high temperatures. Growing rice varieties at high temperatures increased plant height but reduced reproductive growth and seed quality. Foliar application of osmoprotectants like boric acid and salicylic acid mitigated the adverse effects of high temperature on seed production by improving pollen quality, enzyme activity, and seed yield. Seeds from plants treated with boric acid showed better germination and vigor after storage. Rice seeds from later sowing dates showed better storability than those from earlier dates.

1. ABSTRACT
EFFECT OF TEMPERATURE ON PADDY SEED PRODUCTION
By
Lakshmiprasanna Kata
Degree : Doctor of Philosophy (Agriculture) in
SeedScience and Technology
Chairman : Dr. M. Bhaskaran, Ph.D.
Special Officer (Seeds)
Seed Centre
Tamil Nadu Agricultural University
Coimbatore – 641 003
2014
The present investigation aimed at studying, the influence of temperature on
germination and the affect of different priming chemicals on germination of paddy seed at
three different temperatures, the effect of temperature on seed production of short and
medium duration cultivars and how best the adverse effect of temperature can be managed
through foliar application of osmoprotectants and secondary metabolites and to find out the
differences in storability of resultant seed and to observe the changes in seed quality
parameters of two sets of 20 IET entries produced at two different sowing dates.
Seven different priming agents (salicylic acid 50 ppm, ascorbic acid 200 ppm, citric
acid 200 ppm, proline 0.2%, calcium chloride 2%, Na2HPO4 100 ppm and distilled water)
were used to treat six varieties of paddy and the resultant seed was subjected to three different
temperatures (30oC, 38oC and 43oC) during their germination. Primed and control seed
exhibited high germination at 30oC and with the increase of temperature reduction was
observed in seed quality parameters. However, the percentage of decrease was very low in
case of primed seed. Among the priming agents, ascorbic acid @ 200 ppm and salicylic acid
@ 50 ppm were found to increase the speed of germination, germination per cent, root and
shoot lengths, dry matter production and vigour index significantly. Treatment with ascorbic
acid @ 200 ppm resulted in the increased amylase activity in five varieties except in case of
CO (R) 50 in which salicylic acid 50 ppm exhibited high enzyme activity. Hence, seed

2. priming with ascorbic acid @ 200 ppm and salicylic acid @ 50 ppm can be recommended to
improve the physiological performance of paddy seeds. Especially it is applicable in the case
of high temperature conditions to alleviate the deleterious effect of free radicals and
subsequently to improve its physiological performance during germination.
In order to investigate the affect of high temperature on the growth and reproductive
behaviour of short and medium duration varieties a study was conducted using short and
medium duration cultivars. Short duration cultivars ADT 43, CORH 3 and the heat tolerant
cultivars N22 and TKM 9 as checks were grown from September to December, 2012 and
medium duration cultivars ADT 46, CO (R) 50, CORH 4 and heat tolerant check TKM 9
were raised from February to June, 2013 under high temperature (ambient + 5oC). High
temperature increased the plant height and stomata number on both the leaf surfaces and
reduced the leaf area and leaf chlorophyll index. Exposure of plants to high temperature also
resulted in early flowering in all the cultivars under study including heat tolerant cultivars
i.e., N22 and TKM 9. Reproductive growth is very much affected by high temperature. Male
reproductive growth starting from the anthers size, all pollen quality parameters like pollen
viability, pollen germination and pollen tube growth were adversely affected by the high
temperature. Number of filled seed per panicle and also 1000 seed weight were reduced
under high temperature conditions. Among the short duration cultivars ADT 43 and among
medium duration cultivars ADT 46 were sensitive to high temperature. Between the two heat
tolerant checks N22 is very effective in tolerating the high temperature compared to TKM 9.
Resultant seed of high temperature grown plants and control plants were subjected to
seed quality analysis except the seed of CORH 3 and CORH 4 (as F2 seed segregates).
Germination per cent of the seed was not much affected by the high temperature. But the
other seedling quality parameters like root and shoot length, drymatter production and vigour
indices. ADT 43 in short duration varieties and ADT 46 in medium duration varieties
registered high reduction vigour indices.
A study was conducted to mitigate the adverse effects of high temperature on seed
production of paddy using the heat sensitive variety ADT 43 and parental lines of CORH 4
i.e., COMS 23A and CB 174 R with the foliar spray of osmoprotectants and secondary
metabolites. The study revealed that application of salicylic acid @ 800 ppm recorded
positive effect on a number of parameters like chlorophyll index, membrane stability and
anther length and width in case of ADT 43 and R lines. Number of germinated pollen on the
stigma and pollen tube length were higher in case of boric acid @ 0.4 ppm and salicylic acid
@ 800 ppm treatments. Exogenous application of these chemicals also resulted in

3. endogenous enzymes activity. Glycine betaine @ 600 µM and boric acid @ 0.4 ppm
treatments exhibited highest activity of catalase enzyme and protein content in case of ADT
43 whereas in A and R lines salicylic acid @ 800 ppm and boric acid @ 0.4 ppm registered
high catalase and super oxide dismutase activity. In addition to glycine betaine, boric acid @
0.4 ppm treatment also resulted in high 1000 seed weight and seed yield plot-1 in ADT 43. In
case of A and R lines boric acid and salicylic acid registered more number of spikelets per
panicle, filled seed per panicle and also 1000 seed weight. The resultant seed of mitigation
treatments of ADT 43 were subjected to 10 months storage and the seed quality was
evaluated at bimonthly intervals where as that of CORH 4 and R lines were subjected to
accelerated ageing. Boric acid @ 0.4 ppm treatment recorded high germination per cent
before and after storage and it also registered high shoot length and drymatter production in
ADT 43. In case of CORH 4 also boric acid @ 0.4 ppm and salicylic acid @ 800 ppm
registered high germination per cent, shoot and root lengths before and after storage. Foliar
spray of boric acid increased the starch accumulation in seeds which resulted in high seed
quality. In R line also similar trend was followed. Histological studies indicated that
salicylic acid @ 800 ppm treatment showed well filled and tightly packed endosperm with
hard peripheral scleranchymatus cells. The presence of hard cells would offer resistance to
leaching of internal solutes thereby it favoured the storability of seeds.
Two sets of IET entries produced at two different sowing dates i.e., June 5th and June
20th when subjected to 12 months storage revealed that with the advancement of storage
period reduction all the seed quality parameters was observed. Early sown set recorded high
initial seed quality compared to late sown entries. However, the rate of deterioration was high
in early sown entries indicating the better storability of late sown entries.