In this article we will discuss about the growth and development of pearlmillet.
Developmental Stages of Pearlmillet:
The ontogeny of pearlmillet is characterised by sequential completion of the following developmental stages:
1. Seed germination.
2. Seedling emergence.
3. Seedling establishment.
4. Tillering.
5. Final leaf stage.
6. Boot stage.
7. Panicle emergence.
8. Half bloom.
9. Fertilisation.
10. Seed set.
11. Milk stage.
12. Soft dough stage.
13. Hard dough stage.
14. Physiological maturity.
Growth Stages of Pearlmillet:
Many of these growth stages cannot be clearly demarcated as they usually overlap. Hence, Maiti and Bidinger (1981) differentiated three growth phases for easy diagnosis by the farmers.
GS 1:
Vegetative phase which includes emergence, stem growth up to panicle initiation and development. Rapid growth allows better plant establishment. Nearly 6-7 leaves are initiated during this period. Tillering indicates end of GS 1. It lasts for 50-80 days depending on the cultivar and the environment.
GS 2:
It is the panicle development phase. Stem elongation, complete expansion of all leaves and ear head formation takes place during this stage. Tillers developed after this stage may not complete all growth stages.
GS 3:
Grain filling stage. It begins with fertilisation of flowers followed by increase in grain weight. It ends with beginning of senescence, all except 3 or 4 leaves are retained till the end. Development of dark layered tissue in hilar region of seed marks physiological maturity.
Dry Matter Production:
The emergence and establishment of seedlings determine total dry matter production of the crop. Rate of germination and emergence were fast, seedlings survival highest and rate of leaf area expansion and dry mater accumulation was greatest at 33°/28°C.
Tillering in pearlmillet can compensate for low plant density due to harsh environment in which the crop is grown. Leaf number is closely related to number of nodes and thus the number of tillers. In well-established crop, tillers mostly contribute to leaf area, dry weight and grain yield.
Tillers which are formed early in the season, generally, produce grain whereas late tillers have the tendency to die while still vegetative. The tillers may die without emerging from the leaf sheath. Death of tillers is largely confined to those with 2-3 leaves, the youngest and smallest.
Decline in tillering is usually observed when the crop reach full light interception and during active internode elongation, suggesting competition for light and moisture might be responsible for tiller mortality. There is linear increase in dry matter accumulation until after flowering followed by a leveling off or apparent decrease. Growth rate is maximum at 25°-27°C and total dry weight at 20°-25°C.
Productivity:
Grain yield in pearlmillet is a function of growth rate, growth duration and harvest index. Growth duration determine biological yield and harvest index determines the proportion of biological yield to grain yield. Biomass production depends on the interception of radiant energy by foliage vis-a-vis leaf area index and conversion of the absorbed energy into chemical constituents.
In a temperature regime of 19°-28°C, pearlmillet canopy required 250-300 degree days above a base minimum of 10°C to reach the phase of rapid leaf expansion, 500 degree days to leaf expansion and 500 degree days to the maximum leaf area index at anthesis.
Relative photosynthetic contribution of different plant parts to the final grains yield of pearlmillet indicate that about 60 per cent of grain yield could be due to as-similarity activities of the ear (10%) and the leaves, (50%) and 25 per cent from leaf sheath and stem surface. Upper 5 leaves largely contribute to grain yield than the lower ones and flag leaf alone contribute 13 per cent as much as the total contribution of all lower leaves below fifth leaf.