Classification of groundnut The cultivated groundnuts have usually been divided into two classes i.e., the erect and prostrate types. The erect types are supposed to be originated from Arachis pusilla and are now known as Arachis hypogaea sub-spp. fastigiata while the trailing or running types are known as Arachis hypogaea sub-spp. procumbens (this is supposed to be originated from Arachis prostrata). The groundnut as such can be classified as erect, or bunch, spreading, semi spreading and trailing types. Growth stages of Groundnut The details regarding the duration for the bunch and spreading types of groundnut to reach various stages of growth from sowing are given below: Development of rainfed pish bunch groundnut Stage of growth DAS Range Commencement of emergence Commencement of flowering Peg elongation and penetration to the soil complete Pod development commences Maturation of pods commence Maturation of most pods complete 8 23 30 35 83 105 7-19 DAS 20-24 DAS 7-15 D 5-6 DP 60 DAF 10-25 D Period of maximum vegetative growth 15 DAF 38-53 DAS   Period of maximum flowering 20-30 DAF 43-53 DAS   Duration of flowering 20-35 DAF - Development of Virginia Runner Groundnut Commencement of emergence Commencement of flowering Peg elongation and penetration to the soil complete Pod development commences Maturation of pods commence Maturation of most pods complete 8 28 38 43 88 135 7-10 DAS 24-30 DAS 10-17 D 5-6 DP 60 DAF 25-45 D Period of maximum vegetative growth 28-43 DAF 59-74 DAF 35-50 DAS 63-81 DAS Two peaks Period of maximum flowering 35-45 DAF 63-73 DAF   Duration of flowering 31-80 DAF -

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Botanical description The groundnut is a member of the pulse or leguminocase family. It is a herbaceous annual with a more or less upright central stem and with numerous branches that vary from prostrate to almost erect depending upon the variety. The groundnut has a taproot with its lateral covering a depth of 35-40 cm and a spread of 30-35 cm of radius. The lateral roots appear on the firth day of germination. The roots bear nodules which appear on the 15th day of germination and they are of the pin head size at this stage. The size and number increases with the age of the plants reaching to about 0.40 cm in diameter and 800 to 4,000 in number. Sometimes number of nodules decline after 80 days of sowing. The groundnut stem is cylindrical, hairy and becomes more or less angular with age. The stem has large pith, which becomes hollow in older portions. The central stem is usually taller and has a few laterals, which form main basis for classification of different varieties and forms. The first two opposite laterals arise from the cotyledonary branches. The stem is covered with small hairs though the degree of hairiness varies in different types viz. the bunch types are normally hairy; the spreading types are sparsely hairy etc. Three types of hairs are found in groundnut, such as long, short and glandular hairs. Glandular hairs are found on the stipules but are completely absent in spreading type. Groundnut leaves are pinnate with two pairs of leaflets borne on a slender and grooved petiole. There is a pair of stipules about 4 cm long with long alternate points which are fused with the petiole for about one half of their length. The leaflets are opposite subsessile and situated closely towards the top of the petiole. The upper pair is larger than the lower one. The shape of leaflets varies from elliptic to ovate to oblong with the entire or ciliate margins, subcardate base and obtuse or shortly mucronate tip. Characteristics of main axis and laterals Main and laterals Types of Groundnut Erect Bunch Spreading Semi-spreading Trailing Main axis Short and erect Long and erect Very short and erect Intermediate between bunch and spreading Medium length and erect Laterals Erect, slightly oblique to main axis but almost parallel to it They are oblique to the main axis Spread horizontally along the ground usually an inch above the ground except the tips Are prostrate upto a few internodes and then begin to ascend in a bow shaped pattern Trail along the ground, they are flat on the ground upto the extreme tip. Flowers (3-5 in number) are produced in the axils of leaves on short reproductive branches. The reproductive branches develop from the leaf axis and they produce scale like leaves whose axis contains flowers. The flowers are yellow, complete, papilonate and sessile. Usually flowering takes place between 24 to 30 days after sowing which is little earlier in bunch type than in spreading ones. The flowering period normally lasts for 3-8 weeks in case of bunch type and 6-10 weeks in case of spreading. The plants are observed to flower till they reach maturity, however, it is influenced largely by the seasonal conditions prevailing during the flowering phase i.e. rain accelerates flowering while drought has its adverse effect on it. The flower opens between 6 to 8 a.m. and fertilization is completed before mid-day after which the flower droops, the corolla closes and the calyx-tube bends down by 4 pm and the flower withers within three days. The peg or gynophore is formed by the elongation of the basal portion of the ovary (which is called stipe) and bends down at such an angle to the stem as to reach the soil in the shortest distance. The growth of the peg is due to the positive geotropism. It is reported that the presence of numerous minute plastids developed after fertilization in the epidermal walls of the pegs is responsible for the geotropic movement. The pegs become visible in about 5-7 days of flowering and it takes 2 to8 days in spreading type depending upon the soil moisture condition and the leaf axil from where the pegs develop. The young pegs contain white deciduous hairs, which disappear after a few days. On 25th day after flowering the shell of the pod is formed along with a tiny kernel at the stalk-end embedded with a fleshy mass but after a week’s time the beakened kernel starts developing. On 39th day after flowering only beak-end remains fleshy and the kernels show traces of purple pigments. On 60th day after flowering, the shell becomes creamy yellow and kernels become hardened. Now the pods become physiologically matured and are ready for harvesting. For an ideal pod development alternate spells of dry and wet weather are essential which may be obtained by early showing. Heavy rains in early growth phase are necessary for good flowering but there must be no water logging. The pod formation and development of groundnut is greatly influenced by fertilizer application. Line application causes better nodulation and pod development. L-NAA has a marked effect on pod formation and development when applied at flowering stage. This reduces the flowering period, increases fertility of genophores, improves pod size and thus results in a higher pod yield. L-NAA is commercially available in the form of planofix and vardhak, which may be, applied at 40 ppm about 40 days after sowing for higher yield.

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