No abstract

Liew J, Andersson L, Boström U, Forkman J, Hakman I & Magnuski E (2012). Influence of temperature and photoperiod on sprouting capacity of Cirsium arvense and Sonchus arvensis root buds. Weed Research.52, 449–457. Summary Timing of treatment is a key to successful and sustainable weed management. For perennial weeds, highly energy‐demanding, repeated stubble cultivation or tillage is a common strategy in organic agriculture. The fragmentation of underground material stimulates root buds to grow and, if repeated, significantly reduces the energy and nutrient resources of the roots. However, the effect might differ depending on variation in sprouting over the season and among species. Here, we studied the impact of different photoperiods and temperatures on sprouting capacity of root buds of Cirsium arvense and Sonchus arvensis in a climate chamber experiment. Two populations of each species, collected in northern and southern Sweden, were used. Plants were exposed to long (18 h), short (12 h) or decreasing (from 18 to 8 h) photoperiods in combinations with high (18/12°C for 16/8 h), low (12/6°C), decreasing (from 21 to 5°C in 4 weeks) or constant high (16°C) temperatures. Sprouting capacity was evaluated based on the proportion of sprouting buds from short root fragments. Neither temperature nor photoperiod affected root bud sprouting in C. arvense, while in S. arvensis, photoperiod seemed to regulate sprouting capacity. The proportion of sprouted buds decreased in short photoperiods, especially if combined with high temperature. In northern conditions, this suggests that weeding strategies based on fragmentation of the root system of S. arvensis will have low efficiency if the autumns are warm.

Summary The three rhizomatous perennials Elytrigia repens, Equisetum arvense and Tussilago farfara are all problematic in Scandinavian agriculture, due to their low susceptibility to soil cultivation. While repeated soil tillage is a fundamental part of the integrated control of these species, it is highly energy consuming and inefficient during periods when little sprout regrowth occurs. Substituting cultivation with mowing will reduce the environmental impact and labour costs, but its efficiency will still depend on the capacity of plants to sprout. Therefore, we studied the seasonal pattern in emergence and rhizome biomass allocation from July to April in six populations for each of the species. Plants were grown outdoors in pots buried in soil and exhumed at regular intervals in a two‐year experiment. In all three species, biomass allocation to rhizomes continued until late in the autumn. Emergence was severely impaired in E. arvense and T. farfara in September–October, while in E. repens, there was no such reduction in the number of emerged shoots. However, in the latter species, the shoot/rhizome ratio decreased and remained low until the plants had been exposed to a period of low temperatures. The increase in shoot/rhizome ratio for E. repens coincided with the resumed capacity to emerge for E. arvense and T. farfara. These results imply that there is no need to repeat a defoliation of E. arvense and T. farfara, if carried out in September–October. However, removal of the aerial plant parts early in the autumn is important to interrupt the upload of storage compounds to the rhizome systems of all species.

Perennial weeds are often controlled by mechanical means, which aim at stimulating axillary and adventitious buds to sprout. This happens when the apical dominance of the main shoot is removed by defoliation or when the underground system is fragmented. By repeating the measures, the result is a depletion of storage compounds, which weakens the plants and reduces their capacity to grow and reproduce. However, timing is critical. Earlier research has indicated that emergence from fragments of Sonchus arvensis cease during a period in autumn, while the seasonal pattern of sprouting in Cirsium arvense appears to be inconsistent. We studied the emergence pattern of defoliated plants with undisturbed root systems, from late summer to early spring. Potted plants grown outdoors were exhumed at regular intervals, put under forcing conditions for 4 weeks, after which shoots above and below soil level were counted and weighed together with the remaining root systems. In both species, the number and weight of emerged shoots decreased during a period in the autumn. In C. arvense, underground shoots were constantly produced during the same period, while fewer underground shoots were present in S. arvensis. For the latter species, apical dominance does not fully explain the effect; thus, endodormancy might be involved. Root weight increased until withering and did not explain the lack of emergence. Our results suggest an impaired sprouting capacity of undisturbed root systems of C. arvense and S. arvensis during September-October, which has implications for the timing and method of control of these species.

Recently, date (Phoenix dactylifera L.) seeds have gained much popularity due to their vast applications that benefit people and the environment, elevated with plenty of research on food product formulation, cosmetics, and medicinal supplements. Date seeds constitute 10-15% of the date fruit weight. Although date seeds are considered waste products, however, they contain many valuable substances such as carbohydrates, oil, dietary fibre, protein, bio-active polyphenol, tannin and natural antioxidants. Thus, valorisation of the date seeds is necessary as the value could be utilized maximally if they are being studied aptly. This study was intended to (i) evaluate the physical properties of beef and lamb in terms of texture, pH, colour, cooking loss, and water holding capacity as affected by date seed powder; and (ii) compare the tendering effect of date seed powder towards beef and lamb. Texture profile analysis indicated significant differences (p≤0.05) in terms of hardness, springiness, chewiness, and gumminess between the different amount of seed powder used in marinated beef and lamb. The lowest pH value belonged to 20 g of date seed powder which was 5.7 and 6.2 for beef and lamb, respectively. The colour of the lamb was found to be significantly different in terms of lightness, redness, and yellowness when date seed powder was used regardless of its amount. Both beef and lamb displayed a statistically significant (p≤0.05) reduction of colour (L*, a*, and b*) from 20 g treatment samples with 29.7 and 26.5, respectively over the control samples. For beef, redness and yellowness demonstrated a significant difference (p≤0.05) for 20 g treatment samples marinated with date seed powder. Both cooking loss and water holding capacity (WHC) was reduced as the amount of date seed powder used was increased. Different amounts of date seed powder affected the physical properties of beef and lamb, while 15 g and 20 g of date seed powder showed a positive result in regards to meat tenderness.