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Panicle and Spikelets

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The terminal component of the rice tiller is an inflorescence called the panicle. The inflorescence or panicle is borne on the uppermost internode of the culm. The panicle bears rice spikelets, which develop into grains.


Fig. 29 - Rice panicle.


The panicle base often appears as a hairlike ring and is used as a dividing point in measuring culm and panicle length. The panicle base is often called the neck.


Fig. 30 - Panicle base (neck).


The panicle axis is continuous and hollow except at the nodes where branches are borne.


Fig. 31 - Panicle axis.


The swellings at the panicle axis where the branches are borne are referred to as the panicle pulvinus.


Fig. 32 - Panicle pulvinus.


Each node on the main panicle axis gives rise to primary branches which in turn bears secondary branches. Primary branches may be arranged singly or in pairs.


Fig. 33 - Secondary and primary branch.


The panicles bear spikelets, most of which develop into grains. These spikelets are borne on the primary and secondary branches. The  spikelet is the basic unit of the inflorescence and panicle. It consists of the pedicel and the floret.


Fig. 34 - Spikelets.


The floret is borne on the pedicel.


Fig. 35 - Floret and pedicel.


The rudimentary glumes are the laterally enlarged, cuplike apex of the pedicel. The rudimentary glumes are the lowermost parts of the spikelet. During threshing, the rudimentary glumes are separated from the rest of the spikelet.


The sterile lemmas are small, bractlike projections attached to the floret. The rachilla is a small axis that bears the single floret. It is between the sterile lemmas and the floret.


Fig. 36 - Rudimentary glumes, sterile lemmas, and rachilla.