Plant morphogenesis

Abstract

Biological organization is to be seen most distinctly in bodily development. It is obvious that, to produce an individual with a specific form and structure, growth must be more rapid in some directions than in others and must form tissues and organs of different character in different places. Embryology has shown how precisely the activities in one part of the developing individual are related to those in every other part. Few happenings in nature are as fascinating to watch as the unfolding and morphology. More commonly and properly, however, it includes, in addition to a discussion of purely descriptive facts as to the origin of form, a study of the results of experimentally controlled development and an analysis of the effects of the various factors, external and internal, that determine how the development of form proceeds. In other words, it attempts to get at the underlying formativeness in the development of organisms and especially to reach an understanding of the basic fact of which form is the most obvious manifestation-biological organization Workers with plants have a number of advantages, however. In plants, permanently embryonic regions, the meristems, are available for study. At the tip of shoot and root and in the cambial layers these are indeterminate and produce new plant structures almost indefinitely. Such meristems are usually numerous or extensive on the same plant so that ample material for the study of development, identical in genetic constitution, is available. Growth and differentiation in the development of a plant are thus continuing processes and not limited to a single and often brief life cycle.Organs such as leaves, flowers, and fruits, which are determinate in growth, pass through a cycle closely comparable to that of individual animals, and morphogenetic problems can also often profitably be studied in them. The fact that they are usually produced in abundance on a single plant is a further advantage, for here the investigator need not be concerned about genetic diversity in his material but can study strictly The Cellular Basis of Growth 33 structures such as tubers and fruits, the greater size is due to an increase in both the number and the size of their cells. Lehmann (1926) found a positive correlation between the size of a potato tuber and that of its cells. Since the increase in cell size was by no means proportional to that in tuber size, it was evident that large tubers have more as well as larger cells. The same relations are found in tomatoes (Houghtaling, 1935). A more detailed study of this problem, in large-fruited and small-fruited races of gourds, was made by Sinnott (1939; Fig. 3-4). Here cell size increases in the young ovary but much less rapidly than organ size, showing that cell division is taking place. During this period there is more increase in cell size in the larger races. The size at which the cells divide steadily increases. At about the time of flowering, however, division in most of the young fruit ceases, first in the central region and then prog...

The evolutionary development of plant body plans

“…Young sporophytes develop within archegonia; 'freeliving' embryophyte gametophytes develop from dispersed meiospores. In both cases, numerous epigenetic factors influence early morphogenesis that fosters dimorphism (Sinnott 1960). If the most ancient sporophytes represent an 'intercalated' multicellular generation, it is difficult to imagine that they were morphologically elaborate -indeed, they may have been nothing more than the functional equivalent of a sporangium (Niklas 1997 Crane 1997a, 1997b) is clearly dimorphic (Fig.…”

Effects of Temperature Gibberellic Acid and Indolylacetic Acid on Root and Shoot Growth of Cutting From Podocarpus Lawrencei Hook F

“…While the factors influencing root and shoot development are undoubtedly complex and imperfectly understood, it is generally considered that specific substances are concerned with the initiation of adventitious root primordia and that the major sources of these substances are the leaves, from which the substances are translocated to the bases of the cuttings (Sinnott 1960). The observations presented here show that, in spite of vigorous shoot growth at the high temperature, root growth was poor; but that when cuttings devoid of root primordia at the end of the first 3 weeks at high temperature (Fig.…”

Mechanism of Male Sterility in Nicotiana tabacum L.

“…It is known that in some fashion the parts of an organism are so related to each other that a change in one affect the rest. Per haps due to a morphogenetic phenomenon-the compensatory correlation (Sinnott 1960) -the suppression of the growth of the stamen primordia appears to result in the compensatory increase in the growth of the gynoecium. It is significant that during its course of development, gynoecium shows a lateral bulge at its base.…”