Optymalizacja jakości rozsady a plonowanie kapusty pekińskiej (Brassica pekinensis Rupr.) oraz wybrane elementy modelowania rozwoju roślin
AbstractThe present work aimed to determine the possibilities of improving the yields of Chinese cabbage (Brassica pekinensis Rupr.) cultivated for spring harvest through optimising the quality of transplants. Experiments were performed with Chinese cabbage cvs. 'Gold Rush F1', 'Optiko Fi' and 'Blues F1' to investigate the effects of three factors: chilling of transplants (2003-2005), transplant age (2003-2005) and volume of cells in plug trays (2003-2004), on the growth, yield and nutritional value of plants. Before planting out to the field at the Mydlniki Experimental Station near Krakow (Poland), the glasshouse-grown transplants were exposed to natural low non-freezing temperature (during 2 production terms: early and late spring) or they differed in age (20-, 30-, 40-day-old) and root volume (53 and 25 cm3). The studies included also modelling of the growth and development, earliness, bolting and yielding of plants, mainly on the basis of thermal conditions and time. Chilling markedly delayed the growth, decreased the fresh matter and increased the proportion of thy matter in fresh matter and the soluble sugar content of transplants. The amount of chlorophyll "a" and "b" in chilled transplants was statistically lower only in the earlier production term. The chilling of transplants caused an increase in the total and marketable yield of Chinese cabbage by 13.93 and 11.71 t • ha-' (early spring — Pt term) or by 11.55 and 9.51 t • he (late spring — 2nd term), respectively. During early cultivation only 2.1% of plants previously treated with low temperature had external bolters. No premature bolting was observed in late spring or in control plants in earlier cultivation. The proportion of heads with internal flower stalks was 41.1% (2nd term) to 93.2% (1" term) for Chinese cabbage produced from chilled transplants; control plants formed such flower stalks only in the very early cultivation (13.6%). However, internal flower stalks were mostly small and their presence did not adversely affect the compactness or shape of heads, consequently the marketable quality of Chinese cabbage. At harvest, the heads of cabbage grown from chilled transplants had a lower proportion of dry matter in fresh matter and a lower content of crude fibre, as compared to control plants. They also tended to contain decreased levels of chlorophylls, carotenoids, soluble sugars and L-ascorbic acid (statistically confirmed for some of the cultivation periods). The number of leaves and the fresh matter of transplants increased with their age, whereas the proportion of dry matter in fresh matter decreased. Plant height as well as leaf area, width and length were highest in 30-day-old plants; shoot size was smallest in the youngest (20-day-old) transplants. The plants grown from the latter produced a significantly lower total and marketable yield. Compared to that, the marketable yield of Chinese cabbage transplanted at 30 days of age was 20.3% higher (highest among all age groups of transplants) and the average weight of head was 15.5% heavier. At harvest, the heads of Chinese cabbage from the youngest transplants showed the highest proportion of dry matter in fresh matter and the highest content of soluble sugars and thiocyanates, while those from 30-day-old transplants had generally more chlorophylls and carotenoids. The L-ascorbic acid content of harvested plants increased with transplant age. As a rule, using a larger cell volume of plug tray (53 cm3) increased the height, number of leaves, and leaf area, width and length of transplants as well as the shoot fresh matter, compared to plants from smaller cells (25 cm3). The proportion of dry matter in fresh matter was higher in transplants produced in smaller cells. Chinese cabbage transplanted from larger cells showed a significantly higher total and marketable yield (by 5.6 and 6.6%, respectively), heavier heads (by 6.9%, on average), and better earliness. At harvest, plants from smaller cells had a higher proportion of dry matter in fresh matter and a higher content of soluble sugars and thiocyanates. On the other hand, the amount of chlorophyll "a", chlorophyll "b" and carotenoids as well as the chlorophyll "a" : "b" ratio in cabbage heads were higher for plants of larger rooting volume. There were no considerable differences in L-ascorbic acid and crude fibre content with regard to the size of containers used in transplant production. Polynomial regression models of growth based on time (DAS — days from sowing) were proposed for chilled and control Chinese cabbage transplants produced in two terms (early and late spring) and in cells with different volume. Similar models (but based on DAT — days after transplanting) were created for plants grown in the field. The linear regression equation which included thermal time, i.e. growing degree—days, was found to well simulate the leaf growth of transplants (precision above 92%). To develop around 6 leaves, the plants should receive 311.6°D on average in the early production term and 259.8°D in the later one. The earliness of this crop can rather be estimated as a function of thermal time accumulated from emergence (R2 = 0.680) than that accumulated from transplanting (R2 = 0.401). Using a regression model built on the basis of the minimum temperature of transplant chilling and the mean temperature of air during vegetation in the field offers a real possibility of estimating the number of heads with internal flower stalks (the predicted values fitted the observed values in 91%). For cv. 'Gold Rush F1', exponential regression provided the best fit for the relation between the number of plants with external flower stalks and the duration of transplant exposure to temperatures below 2.5°C. A simple regression model describing the marketable yield of Chinese cabbage as a function of thermal conditions (minimum temperature of transplant chilling and air temperature in the field) can predict the yield with 75% accuracy. As shown by linear correlation, air temperature positively influenced the growth of Chinese cabbage transplants, but negatively affected their dry matter and soluble sugar content (expressed as % f.m.). Air and soil temperatures during field production had a positive effect on the thiocyanate content and a negative influence on the chlorophyll "a" and carotenoid content as well as chlorophyll "a" : "b" ratio of mature heads. Strong relationships between the morphological features of transplants and the yield of Chinese cabbage were observed and proven statistically. Moreover, the content of pigments in juvenile plants was positively correlated with their level in mature heads, while higher level of soluble sugars in transplants had a negative effect on the accumulation of both chlorophylls and carotenoids in harvested plants. The results of the studies led to some conclusions that may be useful for horticultural practice. Higher yields of Chinese cabbage can be achieved through chilling of transplants. The treatment, however, is associated with the risk of premature bolting of plants. Duration of plant chilling and temperature level should be adjusted to a specific Chinese cabbage cultivar. The optimum transplant age and cell volume of plug trays is 30 days and 53 cm', respectively. However, using transplants from plug trays with smaller cells led to relatively small decrease in yield. For this reason, they can be recommended, especially for the large-scale production. Developed models, described in this study, can be an important element of Chinese cabbage production planning, and assist decision—making processes of vegetable growers. These models also deepen our knowledge of the relationship between plants and the environment, and contribute to the further development of this field of science.
|Other language title versions||Optimising transplant quality and the yielding of Chinese cabbage (Brassica pekinensis Rupr.). A study with some elements of plant development modelling|
|Publisher||Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW |
|Publishing place (Publisher address)||Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)|
|Publication size in sheets||8|
|Citation count*||3 (2016-05-26)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.