The Contribution of Different Organs to Grain Weight in Upland and Swamp Rice

The contribution of dry matter was significantly greater inthe ears of Dima than that of Kindinga. The flag-leaf lamina,flag-leaf sheath and peduncle, lower leaves and stem of Kindingamade greater contribution of dry matter in the grain at harvestthan those of Dima. On the average of the two varieties 23 percent. of the dry matter in the grain at harvest originated fromphotosynthesis in the ears; 60 per cent. came from photosynthesisin the flag-leaf lamina and sheath and peduncle and 17 per cent.from parts of the shoot below the flag leaf.     

Effect of staking, nitrogen and potassium on growth and development in lesser yams: Dioscorea esculenta

Dry-matter accumulation was greater in staked than in unstaked plants of the lesser yam (Dioscorea esculenta). Staking, N and K application tended to increase the proportion of dry matter diverted into the tubers. Staking was the most important factor in increasing total tuber production, which was one and a half times greater in staked than in unstaked plants. Leaf-area development was closely and positively related to vine growth, and since staking and N application encouraged vine growth these treatments therefore led to the production of plants with greater leaf area. Leaf-area duration was increased by staking and N application and was closely and positively related to tuber yield. Staking and N application increased tuber number per plant while K application increased the size of individual tubers. Staking and K application increased bulking rate and both treatments increased the period of bulking by causing earlier tuber initiation.     

Comparative Growth-rates of Upland and Swamp Rice Varieties

The growth of swamp rice (Dima) and upland rice (Kindinga) wasstudied under tropical glass-house conditions in Trinidad. Kindinga ultimately attained greater dry weight and height thanDima but the total number of leaves and tillers per plant weregreater in Dima than in Kindinga. Kindinga had a greater numberof leaves, on the main shoot, than Dima. Growth curve of leaf-lamina area per plant was similar to thatof leaf-lamina dry weight in both varieties but leaf area perunit dry weight of lamina and per plant were usually greaterin Kindinga than in Dima. Over the whole period, the mean relative growth rate, leaf weightratio were greater in Kindinga than in Dima but net assimilationrate was greater in Dima than in Kindinga. Total nitrogen content was greater in Dima than in Kindingaduring the tillering period but later the reverse was the case.The rate of nitrogen absorption was high in both varieties duringthe tillering and reproductive phases. Split applications ofnitrogenous fertilizer are therefore suggested. The rate ofnitrogen absorption was, however, greater in Dima than in Kindingaduring the tillering period and latter half of the reproductivephase.     

Effects of defoliation on growth and yield in groundnut (Arachis hypogea), cowpeas (Vigna unguiculata), soyabean (Glycine max) and green gram (Vigna aurens)

Defoliation reduced the dry weight of stems, pods, grains and size of individual grains in all four of the legume crops studied and the dry weight of flowering inflorescence stalk in the case of cowpeas and green gram only. The adverse effect of defoliation was more pronounced when defoliation was complete than when half of the number of leaves were removed. The greatest reduction in grain yield occurred when the plants were defoliated during the early podding stage, the percentage reduction being 59.7, 79.0, 86.4 and 95.3 in groundnut, cowpeas, soyabeans and green gram respectively when completely defoliated at this stage and 43.3, 14.0, 42.4 and 46.1 respectively when only half defoliated. The results show that assimilates produced by the leaves during the early stages of growth are used in the growth of stems and leaves, but the assimilates produced during the reproductive stage are used mainly for the growth of the pods. In groundnut, pod number and grain weight were positively correlated with stem weight. It appears that defoliation reduced pod number by depressing the growth of stems and this in turn reduced the number of flowering nodes. The reasons for the differences between the crops in their response to the defoliation treatments and the practical implications of the findings in relation to pest and disease control and plucking of leaves for human consumption are discussed.     

Water and Nitrogen Uptake in Upland and Swamp Rice

The water uptake per unit dry matter and nitrogen uptake perunit water absorbed of swamp rice (Dima) and upland rice (Kindinga)at three nitrogen levels equivalent to 23.6, 70.8, and 118,kg./ha. (20, 60 and 100 lb./acre) respectively were studiedunder tropical green-house conditions in Trinidad. The water uptake per unit dry matter produced was significantlygreater in Kindinga than in Dima at the three nitrogen levels.Additional nitrogen increased the water requirement of Kindingabut decreased that of Dima, the greater increase in Kindingabeing attributed to increase in leaf area. The efficiency of nitrogen absorption in terms of water transpiredwas greater in Dima than in Kindinga at the three nitrogen levels.