Certain properties of hypocotyl of Impatiens balsamina reflecting physiological complexity

Abstract

In the course of a studly of leucoanthocyanin synthesis in balsam hypocotyls (1) certain properties of specific regions of the hypocotyl were noted which were of particular interest. For example, if 5 cm hypocotyls from dark-grown plants were cut into ten segments of equal length and transferred to White's medium with agar and sucrose in light, the time-rate -of appearance of anthocyanin pigment was correlated with the origin of the segment. The upper segments (nearest the cotyledons) were the first in which anthocyanin appeared. Little or no anthocvanin formed, even in strong light, in the absence of sugar, but when sugar was present some pigment appeared in the absence of light. The combination light + sugar (sucrose, in this instance) yielded the most pigment. Surprisingly, in darkness with sugar, the pigment was not formed in segment 1 (adjacent to the cotyledons) which, in light, was the most efficient anthocyanin producer. Furthermore, segments of the hypocotyl differed in their ability to form hairs or lateral roots. Other manifestations, similar to the above, of the responsiveness of the balsam hypocotyl, together with additional practical advantages which will be enumerated, suggested that this species would be a good choice for a comprehensive study of growth and differentiation of the hypocotyl. The hypocotyl has been relatively neglected in favor of simple linear systems such as the root, but the complexity of the hypocotyl provides some problems of peculiar interest. For example, the hypocotyl is transitional between root and shoots, and undergoes extensive growth of essentially intercalary nature. Noel (13) has studied the site of growth in the balsam hypocotyl, using india ink markings. He also studied lateral root and epidermal hair formation in this species. He reported that at any stage 90 % of all subsequent growth occurred in the first 5 or 6 mm below the cotyledons. The region of active growth includes the hypoootyl arch which remains curved in darkness. Noel referred to the region as a pseudo-meristem. In our own investigation, numerous mitotic figures were observed through the hypocotyl arch of 10-day old seedlings. I Received Feb. 23, 1961.The balsam hypocotyl is a rich source of leucoanthocyanins; genetic strains are available w\vhich are anthocyanin-free or which differ qualitatively in the form of anthocyanin present (2). The hypocotyl therefore provides an excellent system for studving the physiology and biochemistry of anthocyanin synthesis while anthocyanin represents a labile overt physiological indicator, i.e. anthocyanin synthesis is quantitatively affected by numerous and diverse environmental factors.This initial paper includes information of essentially descriptive nature plus a series of experiments on pigmentation and root and hair formation in hypocotyl segments in light and darkness with and without addition of the sugars, sucrose and glucose. All data reported here are from seedlings with a hypocotyl length of about 50 mm. METHODSVaughan Seed Company's Scarlet Balsam (f1;...

Chemical Factors Affecting Anthocyanin Formation and Morphogenesis in Cultured Hypocotyl Segments of Impatiens balsamina

“…Definite relationships have been shown to occur. Anatomically, the axis of the hypocotyl of Impatiens balsanzina L. has been shown to present a gradient of tissue types from meristematic at its upper end to highly differentiated and specialized types toward its basal end (3,8). Therefore the various physiological responses, as well as the morphogenetical manifestations observed in cultured hypocotyl segments, can be interpreted with reference to the basic structure and level of differentiation of the tissue.…”

“…Cultured segments of balsam (Impatiens balsamina L.) provide excellent material for the study of anthocyanin formation as an indicator of metabolic conditions accompanying differentiation (3). A similar approach to studying morphogenesis has been taken by Klein and Hagen (7) using cultured balsam flower petals.…”

“…Allan W. Arnold was supported by a National Defense Education Act Fellowship. 3 Present address: Department of Botany, Brown University, Providence, Rhode Island. 10-5 M) and compounds reported to affect anthocyanin synthesis; benzimidazole (3.0 X 10-3M), 8-azaguanine (3.0 X 10-5 and 3.0 x 10-6 M), and riboflavin (3.0 x 10-4 and 1.0 x 104M).…”

“…Quantitative estimates of total anthocyanin formed in the hypocotyl segments at the end of the 10-day experimental period were determined as before (3).…”

“…The seeds were germinated under sterile conditions in total darkness for 7 days as previously described (3).…”