No abstract

Individual segregants, as well as uniform F6 to F8 lines, originating from one group of spring wheat (Triticum aestivum L.) crosses, had a series of striking characteristics setting them apart from the typical spring type. Tillering was limited, and in some lines nearly all of the plants were uniculms. Spikes were large and proliferous with maximum expression of 30 spikelets per ear, and 62.5 mg per kernel, and 12 florets and nine grains per spikelet have been recorded either in individual segregants or for certain lines. Vegetative parts were robust and vigorous, including broad, thick, dark green leaves, thick, stiff straw, and thick, large rachises, glumes and lemmas. Harvest index was higher than in a standard cultivar of regular growth habit. This complex set of characters typified plants of the new type only when grown in short (but increasing) day length and low temperature conditions (Mediterranean winters). Tests indicated a special thermo‐photoperiodic sensitivity in this material. Plants or lines included a wide spectrum of agronomic types with respect to plant height, size and quality of grains, and morphology of spikes and vegetative parts. The normal (2n = 42) chromosome complement of T. aestivum was found in 10 randomly sampled unicum plants.

No abstract

No abstract

Abstract. Diffusetes from seedlings and root exudates from 6-week-old plants of a monoecious line of cucumber, Cucumis sativus L., contained considerably higher levels of gibberellin.(GA-)like substances than did those from plants of an isogenic gynoecious line. Most of the GA4ike activity was found in a chromatogram region ty.pical of GA1 and GA3; some activity, particularly in root exudates, appeared also at an RF similar to that of GA4 and GA7.When seedlings were treated with 3H-labeled GA1, more radioactivity was found in the diffusates from monoecious seedlings than from gynoecious ones. The same was true of biological activity in root diffusates from older plants which had been treated with gib-!erellin A4+,.In conjunction with evidence present in literature, these resulits support the idea that endogenous GAs play a part in the regulation of sex expression in cucumber, relatively high levels favoring the formation of staminate flowers.Auxins have long been known to enhance the female sex "tendency" in cucumber, that is, to promote the formation of pistillate flowers (14). Gibberellins (GAs) have the opposite effect, favoring the formation of staminate over that of pistillate flowers (4) and moreover inhibiting the further development of the latter (Atsmon, unpublished data).These findings were obtained with exogenous hormones. However, in the case of auxin, both, indirect studies concerning relations between growth rates and sex expression (2,7) and direct analvses of the auxin content of plants with different sex expression (8), have provided evidence that this hormone participates in the endogenous regulation of sex expression in cucumber.In the case of GAs, there is so far only indirect evidence for such an endogenous function. Part of it comes from studies on hypocotyl and internode length in plants of different sex types. These parameters can be used as indicators of the effective endogenous GA level in the plants, and the results show that this level increases with increasing male tendency (Atsmon, unpublished data). Another part of the evidence comes from work with the growth retardants AMO-1618 and OCC (Cycocel) which are known to inhibit GA biosynthesis in plants and which were found to reduce the male tendencv in cucumber (Galun and Lang, unpublished data). The experiments described below were designed to obtain more direct evidence for differences in GA content in cucumber plants of different sex types; and also to determine whether such plants differ with respect to recovery of applied GA, that is, presumably, in their metabolism of GAs.Both types of experiments were done with 4-dayold seedlings and with 6-week-old plants. In the seedlings, we determined the quantities of GAs, either endogenous or applied, diffusing from the shoot into agar blocks. In the older plants, the GA content of root exudates was determined, this latter approach being based on the discovery that root