Tall Growth Research Articles

Varietal traits limiting the grain yield of tropical maize II. The growth and yield of tall and short varieties

Abstract Four isogenic varieties with different heights, derived from the Tuxpeno population, were grown in the tropics to evaluate their potential productivity. Short varieties were developed by two means: incorporation of the brachytic-2 gene and current selections of shorter plants. The tallest, original Tuxpeno produced the highest yield, next was the short-plant selection, while the brachytic varieties yielded least. Yield differences between the original and the short-plant selections were derived from the kernel size and the differences between those and the brachytic varieties, from the number of kernels. Incorporation of the brachytic gene is unlikely to improve the productivity of varieties because it results in low efficiency of leaves in dry matter production during ripening, caused by the limited sink size and the compact distribution of wide leaves.

Primary Root Elongation of Three Weed Species

Primary root elongation of prickly sida (Sida spinosaL.) at pH 5.5 was similar to that at pH 6.5 while sicklepod (Cassia obtusifoliaL.) was reduced to 62% and tall morningglory [Ipomoea purpurea(L.) Roth] to 87% of that at pH 6.5. At pH 5.1, root elongation of prickly sida was reduced to 77% of that at pH 5.5. Some elongation was observed in the pH range of 5.1 to 6.5 for all species. Maximum primary root growth of tall morningglory, sicklepod, and prickly sida occurred at approximately 32° which was similar to that for cotton (Gossypium hirsutumL. ‘Empire’). Temperature as high as 39° did not significantly reduce root elongation of sicklepod. Tall morningglory root growth was reduced approximately 50% by 0.2 ppm of trifluralin (α,α,α-trifluro-2,6-dinitro-N,N-dipropyl-p-toluidine). In contrast, sicklepod and prickly sida root growth was reduced only slightly by 1 ppm of trifluralin.

The growth and yield of tall and short sorghums in Nigeria

SUMMARYA Nigerian, long-season, sorghum produced 15 tons of dry matter/acre in about 155 days, but the grain yield was small (2000 lb/acre or 2242 kg/ha) because only part of the dry matter formed after heading went into the grain. In contrast, an American, short-season hybrid which formed only from one-half to one-third as much dry weight as Farafara, gave over 4000 lb of grain/acre (4484 kg/ha) in 100 days. A Nigerian sorghum of intermediate height and a long-season hybrid, produced by crosses between Nigerian varieties and an American, short-season sorghum, gave larger yields than the tall variety because they formed more heads/unit area and more grains/head.Crop growth rates of the three long-season sorghums sown in June increased to a peak in July, but declined sharply to very small values in September, and then increased again very rapidly at the end of September as heads emerged. The most important factors causing the decline were a decrease in radiation and a loss in dry weight from decay and detachment of dead leaves. An increase in radiation at the end of September and developmental changes associated with head emergence contributed to the increase in growth rates just before heading.A large proportion of the dry weight formed after heading in Farafara accumulated in the stem but a smaller proportion in the other long-season variety and the longseason hybrid. There was an inverse relationship between the increase in stem weight and the yield of grain. For large grain yields, sorghums are needed that will produce heads with sufficient grains to accommodate all the assimilate that the leaves produce at the end of the rains when crop growth rates are increasing.

SOME OBSERVATIONS ON THE SITATUNGA IN KENYA

SummaryA 16‐month study was made of sitatunga in a swamp in western Kenya, with particular reference to distribution within the habitat, daily activity, and food preferences.Absolute figures for density could not be obtained because of observational difficulties, but there was a minimum of 7.3 animals/linear km of swamp, or c. 55/km2. The sitatunga preferred areas of swamp adjacent to patches of gallery forest, and areas where there was deep water and a dense growth of tall reeds.They were most active during the first five and last two hours of daylight, and at night. Much of this time was spent feeding. Feeding behaviour and food preferences were studied. The sitatunga usually moved along well‐marked tracks through the swamp vegetation; some of these led to beds of flattened plants, raised above water level, which were probably used for resting and for breeding. The latter took place in most months of the year, with a possible peak in November. Calves remained hidden for some weeks after birth.Group size and structure were examined; most sightings were of single animals or groups of two. A majority of these two groupings were composed of adult females. The proportion of immature animals seen indicated a healthy population.Courtship behaviour was observed 18 times and mating once.

Our hardy Hibiscus species as ornamentals

As a common plant name, "Hibiscus" is more often applied to the showy tropical sorts, especially Hibiscus rosa-sinensis L., than to other species of the genus. There is, however, another equally showy group, the hardy herbaceous mallows, native mostly to the Eastern United States. This group includes Hibiscus moscheutos L., H. militaris Cav., H. coccineus (Medicus) Walter, H. grandiflorus Michx., H. lasiocarpus Cav., and their many garden hybrids. The various species in this group are commonly called Rose Mallows. They grow naturally in marshy areas of the Atlantic States from southern New England to Florida, also inland along rivers and lakes. Isolated populations appear in areas such as the Sacramento River Valley of California. The tall vigorous growth of Rose Mallow plants plus the abundantly produced, large, gaily colored flowers makes them a conspicuous and attractive feature of the vegetation. Hibiscus moscheutos most often occurs in almost pure stands along tidal rivers of the mid-Atlantic states. During the peak of flowering, late July to mid-August, these stands are a striking sight to behold. In spite of the large fleshy roots, Rose Mallow plants withstand transplanting easily even when in full flower. They are also readily groxvn from seed and will flower the first season if sown early. Unlike their woody tropical relatives, the Rose Mallows are herbaceous perennials, and the plants become somewhat coarse by the end of the growing season. They also lack the yellow and orange flower colors so prominent in many Hibiscus rosa-sinensis clones. Nevertheless, the various species have been cultivated as ornamentals in the United States since Colonial times. As cultivated plants they perform best when grown in good garden soil with moderate amounts of water.

Grafting and Gibberellin Effects on the Growth of Tall and Dwarf Peas

Tall peas var. Alaska and dwarf peas var. Progress No. 9 were grafted onto their own roots or reciprocally grafted to determine the rootstock effect on the growth of the stem. In all cases the grafted stems grew the same as their ungrafted controls regardless of which rootstock they were grown on. When similarly grafted plants were supplied with gibberellic acid, good graft unions did not inhibit its translocation. This evidence supports the thesis that the mechanism controlling stem growth in peas is located in the stem and that the roots have no direct control over this mechanism.

Differential effect of 2-chloroethylphosphonic acid on light- and dark-grown tall and dwarf peas

Tall (Alaska) and dwarf (Progress No. 9 and Early June) peas, Pisum sativum L., grown in the light showed a differential elongation response to 2-chloroethylphosphonic acid (CEPA), only the tall plants being inhibited. CEPA was applied either during seed imbibition or in a postemergence spray. In darkness, CEPA inhibited growth of both tall and dwarf peas, especially the former.

Thrush predation of an experimental population of the Snail Cepaea nemoralis (L).

(i) The experiment described in this paper was designed to investigate Sheppard's (1951) results which showed that thrushes predated individuals of G. nemoralis selectively, and further that the relative disadvantage of the yellow morph changed with the changing colour of the background. (ii) Because of the scarcity of thrushes only a relatively few individuals were predated. The predation was much later in the year than in Sheppard's experiment, probably because of the differences in weather conditions. (iii) The results of the experiment indicate that yellows are at a disadvantage during the summer months in the area under investigation, probably because there is a dense and tall growth of herbs in the area and this gives rise to a dark background near the ground. (iv) These results are similar to those obtained by Wolda (1963) who could not explain them in terms of the colour of the background. It seems likely that the present explanation could account for his results. (v) A comparison of the yellow morph-frequencies of predated samples removed from the area before the present experiment was begun, with those in the predated sample from the original natural population found by Sheppard 12 years previously show very little difference although the addition of Sheppard's experimental population changed the frequency of this morph considerably. It is therefore suggested that systematic processes play a large part in determining the population genetic structure.

Rekognoscering i Abu Dhabi

Rekognoscering i Abu Dhabi