264 



GROWTH HORMONES IN PLANTS 



Peas, 62 



(See also Pisum) 

 Pekelharing, C. J., 202 

 Pellia, 63 

 Penicillium, 62 



Peptone, occurrence of growth sub- 

 stance in, 63 

 Permeability, and growth-substance 



transport, 162, 196 

 Perry, J. T., 77 

 Pfeffer, W., 10, 108, 109, 111 

 Phalaris, 3, 172, 173 

 Phaseolus, 25, 60, 75, 95, 97, 165, 



193, 214, 215 

 Photodynamic action [see Phototro- 



pism, dyes in) 

 Photographic records, 32 

 Phototropism, in Avena coleoptile, 

 131-163, 13 

 Blaauw theory of, 146-150 

 compared with geotropism, 185- 



186 

 concentration of growth substance 

 and growth rates in, 152-155 

 course of curvature during, 143- 



146, 145 

 definition of, 131 

 direction of stimuhis transmission, 



139 

 displacement of growth substance 

 during, 155-159, 152, 153, 

 154 

 distribution of sensitivity to light, 



133-135, 164 

 dyes in, action of, 160-161 

 electrical potential and growth 

 substance transport in, 159- 

 160 

 explanations of, growth substance, 

 150-161, 165-166 

 other theories, 161-163 

 growth rates during, 143-146, 



146 

 incisions, effect upon stimulus 



transmission, 7, 8, 137, 138 

 intensity of stimulus and, 141-142 

 light-gradient in Avena during, 

 131-132 



Phototropism, light-growth reaction 



(Blaauw Theory) and, 146-150 



in Phycotnyces sporangiophore, 



166-167 

 positive and negative curvatures 



in, 140-146 

 quantity-of-stimulus principle for, 



139-140 

 in Raphanus hypocotyl, 165-166 

 spectrum sensitivity in, 135, 136 

 transmission of stimulus in, 135- 

 139, 164-165 

 direction of, 139 

 incisions, effect upon, 7, 8, 

 137, 138 

 unequal distribution of growth 

 substance during, 152-155, 

 152, 153, 154 

 Phycomyces, 102, 166-167 

 Physical properties of growth sub- 

 stances, 51 

 Physiological activity of growth 



substances, 52-55 

 Physiological regeneration, 22, 58, 



89-90, 206 

 Piccard, A., 172, 188, 200 

 Pine, 60 



Pisek, A., 17, 87, 147 

 Pisum, 34, 66, 100, 184, 207, 209 



(See also Peas) 

 Plant unit, 32 

 Pohl, R., 58, 65, 66, 90 

 Polarity, and anaesthesia, 74 



and transport of growth sub- 

 stance, 72, 75-76 

 Polarized growth, 83, 95, 121 

 Pollen, occurrence of growth sub- 

 stance in, 25, 61, 62 

 PoUinia, 15, 62 

 Popoff, M., 103 

 Populus, 129 

 Potato, 61 



(See also Solanum) 

 Potential, electrical (see Electric 



potential) 

 Pratt, R., 123 



