Extension growth in Primary Cell-Walls with Special Reference to Hippuris vulgaris

A quantitative study of pit-field distribution in the longitudinalwalls of cortical parenchyma shows that pit-fields increasein number continuously during cell division and growth. A considerationof the data in relation to other information on pit-field distributionand to wider aspects of cell-wall extension suggests that pit-fieldmultiplication may be expected to be a characteristic featureof the growth of intercellular cell-wall surfaces in meristemcells.     

Effects of Photoperiod on the Apparent Viscosity of Leaf Cytoplasm in Kalanchoe blossfeldiana. I. A Method for Quantitative Estimation and its Sources of Error

An adaptation of the centrifuge method of determining cytoplasmicviscosity is described, suitable for the examination of leavesof higher plants exposed to different photoperiodic conditions.Leaf segments are centrifuged for several standard periods,usually i, 2, and 4 minutes, followed by immediate fixation,microscopic examination of hand-microtome sections, and thedetermination of the proportions of cells in the mesophyll regionwhose chloroplasts have been displaced. Among factors whichmay cause systematic errors, variations in cell size, chloroplastsize and chloroplast starch content have been found to causerelatively little error. Similarly, changes in water contentwhich cause up to 14 per cent loss of fresh weight have no largeor consistent effect. Significant effects may arise from diurnalchanges, or from differences in ambient and in growth temperature,as well as in leaf age and the region within the leaf that istested; they can all be minimized by appropriate sampling techniques.Any treatment effects revealed by the method are clearly notascribable to viscosity differences alone, but they are likelyto represent real changes in the physical state of the cytoplasm;they are therefore referred to as representing changes in ‘apparentviscosity’.