Panicle Spikelet Research Articles

Precocious flowering and seeding behaviour in tissue-cultured bamboos

BAMBOO flowers only once during its lifetime, dying at the end of its first fruiting season. This monocarpic flowering is intriguing not only in that it occurs after a lapse of 12 to 120 years, but because it is 'gregarious', local populations of bamboo flowering together and then dying. New bamboo plants are produced either by vegetative subdivision or from seed. Breeding of bamboo, however, has proved to be extremely difficult: seed production depends on unpredictable circumstances and events1, and the basis of gregarious flowering, and the causes of death and flowering, are not known. Flowering in vitro has previously been studied by culturing expiants of stem tips, mature stems, roots, petioles, leaves, inflorescences, flowers and so on2–5. Although bamboo plantlets have been formed by means of organogenesis and embry-ogenesis6–8, in vitro flowering has not previously been reported for bamboo. We now report on an in vitro system in which we could consistently induce flowering in the two species of bamboo Bambusa arundinacea Willd and Dendrocalamus brandisii Kurz. Inflorescence expiants containing a panicle of spikelets gave rise to several viable inflorescences on subculture; fertile seeds were also produced. Further refinements to this system could lead to the introduction of breeding programmes to improve bamboo, and to the production of perennial seeds for bamboo, as well as to a better understanding of the physiology underlying flowering behaviour in bamboo.

Biological Effects of Developing Sorghum Panicles in a Meridic Diet on Fall Armyworm (Lepidoptera: Noctuidae) Development

Fresh panicle spikelets of developing sorghum, Sorghum bicolor (L.) Moench, were mixed into a standard meridic diet and fed to neonate larvae of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith). Differences between weights of FAW larvae fed ‘NK Savanna 5’ (resistant) and ‘Funk H-5245’ (susceptible) were found at the preflowering, flowering, milk, and hard-dough stages of development. Addition of 40 or 80 g of fresh immature kernels per 300 ml of diet resulted in significant differences in weights of FAW larvae fed the two sorghum hybrids. No significant relationship was found between tannin concentration of various stages of kernel development and weights of FAW larvae. In addition, no significant relationship was found between tannin concentration and weights of FAW larvae reared on diets containing milk-stage panicles of 12 sorghum genotypes. Chemical(s) within the glumes of the sorghum panicle probably confers resistance.

Weight Compensation of Undamaged Kernels in Response to Damage by Sorghum Midge (Diptera: Cecidomyiidae)

The relationship between level of sorghum midge, Contarinia sorghicola (Coquillett), damage and weight of undamaged kernels, panicle sterility, and kernel weight was investigated in midge resistant and susceptible sorghum, Sorghum bicolor (L.) Moench, hybrid cultivars. A significant inverse relationship existed between the proportion of spikelets destroyed by midges and the weight of undamaged kernels in two of three susceptible hybrids as well as in three of seven case for two resistant hybrids. In only one trial involving a midge resistant hybrid was there a positive correlation between the two variables. However, these relationships were generally not significant at levels of damage below 40%. A significant positive relationship between the percentage of sterile panicle spikelets and of developed kernel weight occurred in half of the cases. Results of this study signify that for midge damage levels near economic threshold levels, the percentage of spikelets damaged by midges was approximately equal to percentage of yield loss—i.e., there was no compensation for midge damage. Partial sterility did not simulate midge damage.

Effects of Resistant Sorghum Hybrids on Sorghum Midge (Diptera: Cecidomyiidae) Biology

Fewer ovipositing female sorghum midges, Contarinia sorghicola (Coquillett), were found on flowering panicles of two resistant grain sorghum hybrids, ATx2755 x RTx2767 and ATx2761 x RTx2767, than on susceptible hybrids, ATx2752 x RTx430 and ATx3042 x RTx2737, on a few occasions during the 1981 growing season. However, these differences in adult abundance occurred erratically and did not follow any apparant pattern. It was doubtful that the resistance of these hybrids could be attributed to an effect on the number of ovipositing midges. Determination of the number of progeny produced per female that oviposited in panicle spikelets of susceptible and resistant hybrids was complicated by competition between midges at high population densities. An interference index was used to compensate for this competition. Midges infesting resistant hybrids produced 50 to 60% fewer progeny per female than midges infesting susceptible hybrids, regardless of midge density. This percentage of reduction became ineffectual in preventing economic damage to resistant hybrids as midge densities reached high levels. There was a slight, but nonsignificant, increase in the developmental time of midges infesting resistant sorghum hybrids. These results suggest that the effects of midge resistant sorghums would be cumulative in reducing midge density through time.

The Inflorescence and Flower in Male Myrica esculenta var. Farquhariana

There are various ambiguities in the interpretations of the male floret and inflorescence in the Myricaceae. Myrica esculenta Buch -Ham var farquhariana (Wall) Chev, as a relatively primitive species in the family, was chosen for detailed study The presence of tertiary bracts in one individual permits the interpretation of the male flower as consisting of only one or two stamens The anatomy of the flower suggests that it is composed of but a single stamen whose single vascular bundle arises from a distinctive pedicellar vascular supply A subtending bract may or may not be present The so-called column has a complete vascular cylinder and is therefore to be interpreted as an ultimate branch of a compound inflorescence There is no terminal floret in such ultimate axes, but rather, the vascular supply of that axis continues beyond the insertion of the floral supplies. The inflorescence is thus open or indeterminate, and is a panicle of spikes and spikelets. Phyllotactic considerations as well as vascular anatomy lead to the conclusion that the ultimate branch of the inflorescence may be reduced to a pseudocymule This suggests that evidence for the "cymule" of the Betulaceae must be carefully reassessed

Yield and Quality of Rice as Affected by Molybdenum Applied With Chemical Fertilizers and Organic Matter

A field experiment was conducted at the field laboratory of the Department of Agronomy, Bangladesh Agricultural University, Mymensingh to evaluate the effect of molybdenum (Mo) with recommenced chemical fertilizer and organic matter on yield and quality of rice cv. BRRI dhan 30. Three levels of Mo viz. 0, 100 and 200 ppm were applied with recommended dose of chemical fertilizers (80, 15, 40, 10, 1.5 kg ha-1NPKSZn) and organic matter as both cow dung and compost. Plant height, number of ear bearing tillers hill-1, straw yield and biological yield were maximum when 100 ppm Mo was applied with chemical fertilizer. Number of total spikelets panicle-1, grains panicle-1, nitrogen content, nitrogen uptake in grain and straw, and protein content in grain were recorded better when 100 ppm Mo was applied with cowdung. Those parameters were minimum when 0 ppm Mo was applied with either cowdung or compost or NPK. The best performance was obtained when 100 ppm Mo was applied either with recommended fertilizers or with cow dung/compost. The performance of rice with 200 ppm of Mo was better than no addition of Mo in respect of yield and yield contributing characters. Key words: Molybdenum, quality, rice, yield. doi:10.3329/jard.v6i1.1653 J Agric Rural Dev 6(1&2), 19-23, June 2008