NITROGEN LEAF-STEM SOURCE AND HEAD SINK RELATIONS IN THREE CAULIFLOWER HYBRID CULTIVARS

Cauliflower (Brassica oleracea var. botrytis) plant nitrogen (N) in-season storage in leaves and stems may be critical to yield and nutritional value of its edible heads.
Cauliflower leaf-stem source and head sink N relations were examined in a 2-site field study in Nova Scotia.
The objectives were to examine the pathway and efficiency of cauliflower plant N translocation from leaf-stem sources to sink heads and to quantify the correlations of cauliflower source/sink N with plant productivity.
The experimental treatments consisted of three cauliflower hybrid cultivars (‘Minuteman’, ‘Sevilla’ and ‘Whistler’) and three post-transplanting N input rates (105+30+0, 105+30+45 and 105+30+90 kg ha-1) arranged in a split-block design in the fields.
The N treatments were applied with four replicates at shoot-tip straightened stage.
Results showed that during cauliflower short heading stage (three weeks), 87% (or 8.4 g plant-1) of total N uptake was found to store in leaves and stems in the second week of heading process.
Leaf-stem N translocation outflows to cauliflower head sinks increased by 96% (from 1.29±0.55 g plant^-1 to 2.53±0.81 g plant^-1) within one week at head maturity, the third week of heading stage.
During the same period, cauliflower head fresh yield increased by 112% (from 331±200 g plant^-1 to 710±277 g plant^-1), which was proportional with increasing head N accumulation.
The marketable heads contained on average 22% of total N uptake (11.4 g plant^-1). The cv. ‘Sevilla’ had the significantly higher leaf-stem N (8.97 g plant^-1) and head N (2.81 g plant^-1) than cv. ‘Whistler’ (P<0.05). The sink/source N ratio was significantly higher in ‘Whistler’ (mean 0.35) than in ‘Minuteman’ (mean 0.29) (P<0.05). Cauliflower leaf-stem N accumulation increased quadratically with head fresh yield (R² = 0.64, P<0.01) and head N accumulation was also quadratically correlated to the head fresh yield with a higher correlation coefficient (R²=0.78, P<0.01). There were also significant interactions between cultivars and N treatments on N translocation from cauliflower leaf-stem sources to head sinks.
It was concluded that promoting N temporary storage in cauliflower leaves and stems before curd initiation could stimulate head N translocation, which could result in reduction of post-transplanting N inputs.

XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Environmental, Edaphic, and Genetic Factors Affecting Plants, Seeds and Turfgrass

Hong Li

Brassica oleracea, head yield, N sink/source ratios, plant N translocation, plant and nutrition correlation

https://doi.org/10.17660/ActaHortic.2012.938.28