As for shade tolerance the growth of Helianthus annuus was ananlysed under various light conditions, in comparison with that of Phaseolus aureus1, 2). 1. The growth of H. annuus in total plant dry weight, leaf weight and leaf area was depressed markedly by shading. Particularly, the depression was striking in deeper shade (5, 10 and 22% light). In H. annuus the highest leaf area occurred in the full (temporarily 75%) light, while in Ph. aureus in light shade. 2. The relative growth rate of H. annuus was evidently depressed by shading and turned to negative in later stage in deeper shade. The net assimilation rate (NAR) decreased with shading, though its variation with plant age was small. 3. The leaf area ratio (LAR) tended to be large with decreasing the light intensity. However, in heavy shade (5 and 10% light) the LAR became smaller than in the 22% light, and this character is fatal to the shade tolerance. 4. The pattern of response of the ratio of leaf area to leaf dry weight (F/F) to light intensity was similar to that of LAR. The ratio of leaf dry weight to total plant dry weight (F/W) decreased with shading. The range of variation with light intensity was larger in F/F than in F/W. 5. The ratio of dry weight of non-photosynthetic organ to leaf dry weight (C/F) became large with decreasing illumination and this tendency was amplified with plant age. 6. In order to confirm the effect of magnitude of C/F and of F/F on dry-matter production, the NAR was calculated on the basis of the photosynthetic and respiratory rate of leaf and the respiratory rate of non-photosynthetic organ using the results of growth analysis. 7. The low shade tolerance of H. annuus may be attributed to the low F/F, which brings about the low LAR, and to the the high C/F under shade.
1. A remarkable outgrowth from the cut surface of epicotyl was found in etiolated seedlings of Stizolobium hassjoo. 2. The attempts to produce such an outgrowth as in S. hassjoo were unsuccessful with Vicia faba and Pisum sativum. 3. The outgrowth has some of the characteristics of plant tumors. a) Its external appearance resembles that of other plant tumors. b) The outgrowth could grow slowly on a medium without addition of growth factor. It seems to be partially autonomous in regard to growth factor. c) It is not differentiated as compared with normal organ, like in other plant tumors. 4. It is a new type of outgrowth different from crown gall, because it is caused without inoculation of Agrobacterium, and formed under aseptic conditions only by cutting epicotyl. The outgrowth naturally differs from genetic tumor or auxin induced tumor. 5. Light seems to be inhibitory to the formation of the outgrowth. 6. When the epicotyl was cut in part (I), no outgrowth was formed from any position of the part. The outgrowth, however, is produced from the lower parts of the epicotyl. This seems to be attributed not to inhibitory principles produced in part (I), but to a complicated reactivity of the cutting position.
The phyllotaxis of a young plant of Physalis alkekengi var. francheti f. bunyardii is spiral with contacts 1 and 2, but an older flower-bearing plant shows a peculiar phyllotaxis, in which a pair of leaves a little different in size from each other (the larger leaf is called a plus leaf and the other a minus one) arise at a node with a divergence angle of about 100° having a flower immediately above between them. Therefore the pairs of leaves at successive nodes are not decussate. All the plus leaves are distributed in an oscillating arrangement on one side of the axis, and all the minus ones in a similar arrangement on the other side. The appearance of the peculiar phyllotaxis depends on the mode of branching. The flower-bearing shoot of this plant is not a monopodium, but a sympodium, i.e. the axillary bud of the plus leaf always comes to place itself at the end of the axis and the terminal part of the axis becomes a single flower between two leaves. Each axillary bud produces only two leaves and then is replaced by the next younger axillary one. Therefore the minus leaf at each node is the first leaf on the axillary shoot of the plus leaf. Namely the flower-bearing shoot of this plant is a so-called anthocladium.
Assimilatory and respiratory changes with age in Pharbitis cotyledons have been investigated in relation to their photoperiodic sensitivity. 1. The development of photosynthetic activity and accumulation of chlorophyll in light are affected by preceding dark periods of germination, and do not parallel with the rise of photoperiodic sensitivity. 2. The rise in the photosynthetic activity is preceded by that in respiration. The photoperiodic sensitivity begins to appear as photosynthetic O2-output balances with respiratory O2-uptake, i.e., compensation point is attained. 3. The photoperiodic sensitivity appears concurrently with the rise in sensitivity of oxygen-uptake to sodium azide, hydroxylamine, arsenic trioxide, malonic acid, sodium fluoride and monoiodoacetic acid.
Evidence for a DNA-mediated interspecific transformation of a root nodule bacterium, Rhizobium leguminosarum with respect to its host-specificity was obtained. The treatment of the bacterium with the DNA extracted from Rh. phaseoli was shown to make the acceptor (Rh. leguminosarum) capable of forming root nodules on Phaseolus plant, a capacity initially lacking in this organism (Rh. leguminosarum). That DNA of Rh. phaseoli is the active principle operative in this transformation is indicated by the fact that the treatment of the active DNA-extract with DNase destroys the transforming activity in question. Boiling of the DNA-extract also destroys its activity.