油菜叶片扩展的功能性需硫量及其作为缺硫诊断的探讨

利用人工气候室进行了双低冬油菜Canola（Brassicanapus L.）苗期的控流试验，以探讨供硫不足条件下对植株不同生长参数动态变化的影响效应。结果表明，单位重量叶面积（即A／W）的变化是反映植株硫营养状况的最敏感指示参数。根据其相对增产率的变化求得了对油菜叶片扩展的功能性需硫（S）量为0.32％。这一数值较传统方法，即采用全株或某一器官的干物重（DM）变化所求得的临界值，能更有效地反映植株（器官）的硫素丰缺状况。当再利用能力较弱的硫元素供应不足时，最先受到影响的是幼叶的扩展速率，而植株（或叶片）的干物量往往因净同化率（EA）和相对生长率（RW）在缺硫后的一定时间内相对增加而产生累积效应。因此，油菜叶片扩展的功能性需硫量可以作为油菜缺硫的诊断指标。

STUDY ON FUNCTIONAL SULPHUR REQUIREMENTS FOR LEAF EXPANSION AND AS A CRITICAL VALUE FOR SULPHUR DEFICIENCY IN OILSEED RAPE

Sulphur(S) supply control to canola-double low oilseed rape (Brassica napus cv.Hyola) experiment was carried out in growth cabinets of phytotron to investigate effect of S stress on growth of the seedlirigs. The results indicated that leaf area and weight ratio (A/W) was one of the most sensitive parameters to S deficiency in oilseed rape. Therefore, the functional sulphur requirements for leaf expansion was obtained from A/W changes with S concentration. Functiorial sulphur requirements determined in this way was more sensitive and accurate than did the critical values determined in conventional one by correlation with plant or tissue dry matter (DM). For nutrients with low mobility, such as S. the young tissue must be affected first when there was a nutrient shortage, the young leaf blade was a good indicator to reflect nutrition status in plants but plant (or leaf blade) DM responded slowly and insensitively because the nutrient deficiency usually depressed leaf blade expansion but increased plant (leaf) DM. Therefore, shoot DM for response to S stress development usually gave it unsatisfled results for setting critical values, these results were correlated with relatively increasing in net assimilation rate (E_A) and relative growth rate (R_W) for S deficiency. The functional sulphur requirements determined by relative leaf expansion rate was 0. 32% while that determined by shoot DM was below 0. 1%. Furthermore, the response of leaf area or length could be seen approximately 10 days earlier than that of DM after reduced S supply.Functional sulphur requiremants can be used as a crllical value for diagriosis of S deficiency in oilseed rape.