L'importance de l'approvisionnement en eau dans la ruche

Résumé Au cours de recherches d'ordre pratique sur la possibilité de claustrer des ruches (1) nous avons été amenés à envisager particulièrement un point important:l'apport d'eau à la ruche claustrée réduit, dans de fortes proportions, la mortalité des Abeilles. Quel est son mode d'action dans ce phénomène? C'est ce que nous allons essayer d'éclaircir dans cette note.     

Nucleic acids in relation to cell division in Lilium longiflorum

Methods are described for preparing cell suspensions of Lilium microsporocytes, microspores and pollen grains; for obtaining cell counts of these suspensions; and for their analysis for pentose nucleic acid (PNA) and desoxypentose nucleic acid (DNA).The results of these analyses have been calculated to nucleic acid content in μμg per microsporocyte, microspore or pollen grain, and the results related to logarithm of flower bud length, an index of the developmental status of the cells, and of their temporal relationship to meiosis, microspore mitosis and opening of the flower.DNA content per cell drops sharply at the end of meiosis, with the formation of four microspores from each microsporocyte. It then increases gradually during the microspore interphase between meiosis and the microspore mitosis. At microspore mitosis DNA content doubles rapidly. In the development of the resulting binucleate pollen grain, from microspore mitosis until the opening of the flower, there is a further gradual increase of DNA content. PNA content of these cells follows the same pattern up to microspore mitosis at a level about twice that of DNA, increases sharply at mitosis, and continues to increase rapidly at a rate nine times that for DNA in the maturing pollen grain.The absolute amounts of DNA and PNA are great. At the time of anthesis the two-celled pollen grain contains about 375 μμg of DNA and 1705 μμg of PNA.